1) Do you enjoy bonus objectives that ask you to find a certain amount of hidden items? For example, in Kingdom Hearts 1 you are tasked to find all 101 puppies throughout the game and there is an item you cannot get unless you get them all. Would you enjoy searching for all of them?
2) See above
3) Super Easy: Setting stuff to lowest difficulty and just blowing things up. Really only for fun and not for challenge.
Easy: Mario Kart and the like. Things that you can pick up and play. Probably not going to fail and if you do, you'll probably get it the next time.
Normal: This game on normal difficulty. Also, most Final Fantasy's are this difficult. For the most part, it's a fair challenge and every so often, there are things that slow you down, but you know you can do it.
Challenging: If you have ever played Cathrine, this is what I'm talking about (on Normal). It might start easy, but by the end it'll take some time to figure out how to do it. You might need strategy guides. Metal Gear Solid in some places hits this and some of the optional bosses in Final Fantasy are like this.
Extreme: If you have ever played Person, this is the difficulty I'm talking about. Also, Penance from FFX International, Ozma from FFIX, Cathrine on max difficulty, and
are good examples of this. Anything that when you see or hear about it you wonder "How is that even possible?"