reactive fire question

[reactive fire question]

If a squad of axis zombies start off hidden then use fast to move two squares and the first square puts it in line of sight of an allied unit within weapon range but the second square the zombies end up on is out of line of sight. Does the allied unit get to interupt the zombies movement and roll for a reactive fire?

[heavy flak grenadiers]

Can Heavy Flak Grenadiers do a sustained attack?

 

[noob LOS question]

If a squad is in the same square as an anti-tank trap can an enemy squad (using normal weapons not close range or artillery) attack it? Or is LOS blocked?

thanks in advance .. (sorry for the basicness of the question)