if tou activate a squad with Yavaris can it attack the same ship or squad and same hull zone twice or does it have to attack different targets?

Yeah there's is nothing to stop you from attacking the same squadron or ship hull zone with a squadron's second attack.

That's that I thought but just wanted to make sure. That makes luke being commanded by Yavaris very deadly against say a glad with its only 5 hull points

Or dutch and his y wing nasty as it cause the imp ship to activate. Which means they can attack that round.

Yea then wedge can shoot after Dutch with 6 blue dice since Dutch activated the squadron

Yea, all of those work. The hard part is setting it all up