The strongest (most powerful) Pokemon is of course rayquaza.
Easiest way to find stronger Pokemon have a decently strong Pokemon first in your party use repel stay in a area and maybe a Pokemon stronger than you will show up.
They don't get sronger, but your Pokemon will get stronger if you battle them a lot.
arceus
Train your Pokemon and level them up by battling.
yes they are
yes because arceus can be any type of pokemon
I believe X is stronger, but Y looks cooler.
brick break
There is no such Pokemon as Mewthree.
Sceptile
No
Guess