1. You can trade Hoenn pokemon if both of the players involved in the trade have the 8th Hoenn badge.
2. You can still trade evolve at level 100, however it's always best to fully evolve a pokemon at level 98-99, don't wait till the very last chance :)
If you need the trade evolution I can help you, on which server are you?
Just as a tip,the players that makes a trade where is involved in trade a hoenn pokemon don't need 8th hoenn badge .For example,i just arrived in hoenn and i bought a gyarados pokemon from hoenn.