So I ran session zero of out home brew setting (kind of mouseguard but with rabbits) tonight for my kids (7&9) and my son declared “I want to be a rabit Mage Riding a Badger around with a giant flaming sword, shooting meteors at our enemies” ... looks like I’ll be testing some of these ideas soon!

1 and 2 have not been asked.
3 and 4 have been answered (no and no).
Edit: For those wanting the exact text, it's the first question in the FAQ.

Overall, this looks really nice.
If you look at the sample settings, each of them either splits Melee or Ranged. Those with Gunnery have 5 combat skills, but otherwise, they're limited to 4 skills. The default fantasy setting doesn't split Ranged, since it's just not dominant enough to justify being two skills. Genesys isn't a simulationist game, so the fact that knowing how to throw a knife is totally different than knowing how to shoot a bow isn't important.
I'd also worry about how fragmented the Knowledge skills are. This can serve a role, where you want different party members to each have their own Knowledge skill, but you run the risk of making each of them insufficiently valuable. Instead, you're likely to just have one player with a high Int that makes all the rolls, and doesn't bother investing XP. I think it's hard to justify more than a couple Knowledge skills without it becoming a trap option, but certainly in a game where the characters are all scientists or scholars, it could work. The playtest had more Knowledge skills, but they trimmed it back to one for the book. In D&D, there are 4 knowledge skills, but those aren't competing for the same XP as the skills that are applicable in combat.
Casting skills don't run into this issue, since players generally only take one of those. If you allow a character to take two different casting skills, the increase in versatility may justify the additional expense in XP. It does mean that you need to design magic systems and flavors for all of them, though.
You may also want to remove Operating, and roll that into Survival (piloting a ship) and Mechanics (operating gnome constructs).
I think players are expected to pick a couple skills outside of their career, but your setting does end up with more skills than normal. That shows up as an issue with the 8 career skills not seeming sufficient, but it will also be an issue when spending XP. Players will need to level more skills, which makes advancement slower, and the initial characteristic spread more defining.
From a formatting standpoint, it's nice to use the skill's proper name (capitalized) when possible, since it makes it clear that you're calling out a specific game term.
I agree that an advantage die on bow attacks is really strong. If this were limited to a variant bow that was lower damage than the normal bow, this would be fine, but I don't think this is the case for Dragonlance. Removing a setback die is better, but that might still be too strong, given that a lot of opponents will have defense, so it's usually applicable.
The low light vision description for the Half-Dwarf mentions half-elves instead. Goblins have a similar issue with half-ogres, and Centaur references elves.
The Minotaur's Brutish Strength, and high Wound Threshold is probably a little too powerful given the XP cost (I think the D&D Dragonlance setting had a similar issue with Minotaur being overpowered). Bonus damage is pretty strong, and even the Centaur's bonus is probably undercosted.

Minor issue, but it looks like the wording of the Augment spell adds an ability die, but doesn't actually increase the ability, so the base damage doubled would only be 8. The extra die does help deal with the difficulty dice. You also have the option to get another 3 from a wand (or perhaps 4 from a staff, though a wand with close-quarters would be more optimal).
Your point is still totally valid.

Also the Attack Spell a Combat Check So it is subject o all the combat modifiers, shooting into Engaged, Dodge, Defense,   Adversary etc. anything that makes hitting with a rifle or sword harder also applies to the Attack Spell.

Snow Crash by Neal Stephenson is a really good inspirational source for how a de-federalised United States could look. However, taking into account Paul Kennedy's theory of Empires, and the slow but observable collapse of the American Empire now, you'd have to work on the assumption the United States is no longer a super power or even world power. It will likely be a middle tiered power and probably under heavy influence from whatever hegemony could viably be a world power in 300 years time. Not China; its time will have been and gone. Possibly Germany, possibly say, Brazil.
I bring this up because having that foreign influence/meddling could be a good plot angle in the same way the Japanese zaibatsu of the William Gibson Sprawl novels were such a good hook. Think how the defection from Maas Biolabs to Hosaka drives the plot of Count Zero as an example.

Most all of the careers have no more than 3 skills linked to the same characteristic.  So, yes, there's a balance issue, but mostly falls under the role-protection rubric. Otherwise, why have the career/non-career distinction at all?  It also nudges players to conform somewhat to the flavor of the setting (instead of everyone just making mage-tanks), but you could just do a away with it -- no one will stop you.
 

The tier 3 Animal Companion talent is another approach to having a bound demon. It's also useful for something like a golem.

Let me help you on what appears to be a fundamental error in your logic:
 
DISCUSSION, noun
"the action or process of talking about something in order to reach a decision or to exchange ideas."
Coming in and saying you have an "awesome" (quoting you here) idea you can't monetise because of Genesys, and because of how integral another system (if it's d20 I will literally laugh out loud) is to your awesome idea.
Not withstanding the merits of the game you've built, the premise itself does not lead to discussion. You are seemingly not interested in talking to people, merely at or past them; your question assumes people take a binary view on your original premise, and that binary viewpoint is driven by assumptions.
You've already had the best response you will get, but it's still not enough to hang a discussion on. @whafrog said it best;
 What actually happened here was you asked a question, framed it as a discussion, disregarded the answer you didn't want to hear, and got defensive. I'm unsure why your expectations were of a better outcome than you got.
 
 

http://www.drivethrurpg.com/product/228813/Genesys-Core-Rulebook

Pretty electrons dancing to my bidding!  The rulebook's here!!!

I read that text to indicate that a single maneuver is sufficient to sustain all existing spells. However, I assume the intent of the rule is that you need a concentrate maneuver for each spell.
Rules Lawyer:
Will spell 1 end? No. They performed the concentrate maneuver during the turn. Will spell 2 end? No. They performed the concentrate maneuver during the turn.

For convenience: https://www.twitch.tv/videos/209100389

For convenience: https://www.twitch.tv/videos/209100389

Unless you tweak things to either add the implement damage bonus to Blast, or use double the Knowledge rating, Blast isn't going to be very effective at clearing groups. I'd suggest the former, since it doesn't vary as much as doubled Knowledge. These two suggestions are from the FAQ.
In D&D, wizards are control, so they're effective against groups of minions, but your Genesys world doesn't have to have them in the same role. The high end of direct damage for the Attack spell is better than the other options, so it might be better to let the archer take out the minions, with his reliable bow that can eliminate one every shot, while the mage goes against the heavy opponent, missing more often, but landing more devastating hits. The crossbow essentially has a base damage of 9, a halberd/great axe ends up at 11, while the Empowered attack spell from a staff ends up at 14 (though it costs 2 strain).
Edit: In any case, I wouldn't tweak the rules unless you're having a problem with them.

If it helps, this was also clarified in the FAQ.

If it helps, this was also clarified in the FAQ.

If it helps, this was also clarified in the FAQ.

Just finished our first session! Here's the recording:
 

That was a quick reply!
One manoeuvre, one spell.

I read that text to indicate that a single maneuver is sufficient to sustain all existing spells. However, I assume the intent of the rule is that you need a concentrate maneuver for each spell.
Rules Lawyer:
Will spell 1 end? No. They performed the concentrate maneuver during the turn. Will spell 2 end? No. They performed the concentrate maneuver during the turn.

Dedication will only take you to 5 characteristic, so I'm not sure how a character would get to 7. A literal reading of Augment is that while you get an extra attribute die on your skill check, you are not increasing your attribute, and therefore would not increase the base damage. Between the two of these, I think you're still capping at 14 damage. I've also read this to imply that you add an attribute die even if your skill is higher than your ability (not upgrading the die), though that may not be intended.
In settings with cyberware, you could potentially bump this to 18 (since you can boost Int to 6 and Overcharge to 7) but this is an uncommon mix. If your setting allows cyberware with magic, I would suggest that you not allow the cyberware bonus to apply to the magic.
In any case, 14 with Burn is very good. Using a magic ring this goes down to 12, and will generally be successful, which is probably about as good as the Sniper Rifle, and better than existing Fantasy weapons. I'd suggest not providing a PC with an Empowered+Burn magic ring.

One thing I have considered is making Forbidden Lore and Scholastic Lore into the two lore skills, and then having a Tier 1 talent which you can take to pick specialisations, providing a handful of boosts or maybe upgrades to a specific topic. 
So you might have a few ranks in the forbidden lore skill, and then a couple of talents that are like, Specialist (Orks), Specialist (Cults), which improve your rolls on those specific subjects. 
 
Thanks for the heads up about all the instances of Mechanics showing up by the way, I'll run a quick find and replace. 

I seem to have expressed my point poorly. While in the setting there are a lot of lore skills, it doesn't work well mechanically to reproduce that in Genesys, since the cost of the skill is the same as the cost of other skills that are more commonly used.
I could be off base on this, and if your campaigns have encounters being won by lore checks more often than combat checks, splitting knowledge up makes sense.
Another approach is to have a T1 talent for access to each forbidden lore, while still having a single Knowledge skill.

This is impressive.
It looks like Tech-Use replaces Mechanics, but there's still a number of mentions of Mechanics.
There's a *lot* of lore skills. I understand that normally, knowing one of these things doesn't get you the other information, but it damages the balance. In a normal campaign with a single Knowledge skill, that skill gets used about as much as another skill like Perception. It's hard to imagine each of the individual lore skills coming into play that often, making them a trap option. They don't have to be as valuable as the combat skills, but they're probably not even close. Perhaps if it was just Lore and Forbidden Lore, it might work better.
Multiple magic skills is fine, since any individual character is generally only going to use one, and they actually do use it a lot. In fact, for the base Genesys setting, the developers figured they'd use it too often, so the mechanics push the player to invest in Knowledge as well.
It may make sense to combine Melee (Light) and Melee (Heavy), like the modern setting. Given how much melee there is in this universe, keeping them distinct is also reasonable.