1) do I need PA training to use PA
2) how can I get remnant PA
3) what is the lvl cap
4) how do I kill mr. house
5) is there an ending that ruins the game(avoid)
6) what's is the best home
7) how can I get unlimited caps
8) where can I get a sniper and a scope
9) is there a ghoul town like the underworld
10) can I still do side quests after the end of main story
11) what do you get for beating the game on the hardest mode
1) Yes you need power armor training to use power armor.
2) Arcade Gannon gives you some. Or you can kill any Enclave Remnant member whilst they're wearing it and loot it off them.
3) Level 50 with all DLC's.
4) Hack the computer next to his Screen, get the elevator down, and you'll figure it out from there.
5) All ending's end the game, there is no playing beyond.
6) Personal preference. I like the sink at Big MT.
7) If your on the PC its pretty easy. If your on a consol, its not exactly unlimited caps, but you can take all the gold bars from The Sierre Madre Vault, they're worth more than I ever spent.
8) The Gun Runners/ Various Enemies.
9) No.
10) You cant play on past the end of the main quest, you'll need to do all side quests/DLC's before you complete the main storyline.
11) Pride ? You get and achievement/trophy for completeing the Main quest from start to finish on hardcoe mode.
I think you should visit http://fallout.wikia.com/wiki/Fallout_Wiki for any further niggling questions.