#bverkade

All of the Blowfly Infestation triggers are put on the stack at the same time and they can all target the same creature. Once the targeted creature dies, the other triggers targeting it will be countered when they try to resolve.

Of course that 5/5 creature dying will also trigger Blowfly Infestation and thus you’ll have to target another creature with that Blowfly Infestation target.

Yes.

Phryexian Revoker’s second ability only functions while its on the battlefield, like most static abilities of permanent cards. Once Phyrexian Revoker leaves the battlefield, its abilities no longer are in effect.

It doesn’t.

Eye of Ugin’s first ability is a cost-reduction effect. It has nothing to do with adding mana to your mana pool and there is literally no interaction with Doubling Cube.

No.

Being printed in Eternal Masters doesn’t change what formats a given card is legal in.

Yes.

No, because it never leaves the battlefield.

When a double-faced card transforms, it stays on the battlefield and just changes to its other face. (It doesn’t go to exile or elsewhere unless the card specifically says that it does so, like with the Magic Origins baby-planeswalkers.)

No.