Lots of questions for one post, Ghion - but I'll take a stab at your main points.

The GP christen Eagle is a beautifull scale plane but leaves MUCH to be desired as an aerobatic platform. In comparison the Ultimate is a much better flying plane. You will need at least a 30cc (1.8ci) glow or 40cc gasoline engine for it. My recomendation would be 2.1 glow or 50cc gas.

Use the search function here on RCU and you will find a ton of useful info on this plane.

For what it's worth, I was so unhappy with the flight characteristics of my GP Eagle I quickly sold it. Pity because it really is a gorgeous airplane.