> I want it to pick every single unit in a unit group not one. I'd like for it to do it so that they where all attacked at the same time as the effects for my skill would look so much kooler but if not then u've alreadly answered my question
Well, the Pick Every Unit function happens all but instantaneously, so treat it like you're applying it for one unit through Picked Unit, and I don't think you'll be disappointed.
3 & 4. Maybe. If you follow these steps:
1. Give some caster unit the ability Crow Form.
2. Take the ability away.
3. Use a trigger to set the caster's Flying Height (Animation triggers).
4. Make it cast some ability.
That should allow you to cast some ability from in the air. You could possibly use the same kind of thing for casting into the air by putting a dummy target unit in the air.
I used a method similar to this in my spell Pillar of Lightning. You might see if you can learn anything from it. It's on The Helper, but here's a link if you want to see it:
http://www.thehelper.net/forums/showthread.php?t=68522
Even if you just look at where the lightning bolt is in the picture, you can see how it's above the ground. That's a dummy caster who had his flying height raised.