Forum:Question about some cards

can someone help me out with something

....ok, let's say my opponent activate prohibition on gb bestiari and i summoned prisma and activate it's affect by sending bestiari to the graveyard from my deck, can i still fusion summoned Gyzarus using Prisma?

....let's say my opponent activate prohibiton on bestiari and i have a bestiari in the graveyard, can i still bring it back from the grave with darius effect and then fusion summon gyzarus?

....If chaos emporer dragon is summoned, do i get to choose whether or not to activate it's effect?

....if i am declaring an attack with a monster, can my opponent activate compulsary evacuation device during the battle phase?

plz help!!!!!