Hello, I am stuck on these reactions: #1 Which mechanism is correct for AlCl3?

Hello,

I am stuck on these reactions:

#1 Which mechanism is correct for AlCl3? I have seen both mechanisms used, but I am not sure why one is favored over the other for certain reactions.

#2 & 3: I am not sure which resonance for each reaction is the correct one. Can someone explain which resonance is the correct one to use when reacting the diene with the dienophile and why?

Thank you!