Questions regarding Evolutions

The Scream 99 stats are not permanent -- they'll only last 7 days and it will again have a 99 boost on the 2nd timeframe in December. As for Evolutions, as long as the upgraded stats on the upgrade don't exceed the stat cap of the Evo, the card should still be able to upgrade. For example, if a card has 80 shooting (85 after the upgrade) but the Evo has a stat cap of 83 shooting, then the upgrade will not +5 shooting on the 83. Instead, it will go from 83 shooting to 85. That's because the stat cap of the Evo was only 83 shooting and the new upgrade exceeds the stat cap -- like rendering the Evo null.

However, in the same example, if the Evo stat cap is 85 then the Evo will still apply after the upgrade and it will add on the Evo's stat upgrade to the card. If the stat cap upgrade on the Evo is for 85 and it increases the shooting by +3, then the upgrade will stack on it and give it a higher stat than intended.

I'm not so sure about your other questions; not sure what happens with Roles, Playstyles, or Rarity.

As you can tell, even the stat upgrade thing is just how I understood it and everything is at your own risk, so thread lightly!