about PSP…?

uhmm.. im about to buy psp…
buy i heard that you can download and play games…
and here are my questions:
1. is it safe to downgrade it?
2. can i still play UMDs if i put custom firmware?
3. if i downgrade it can i still restore it to it's original system?
4. what are pandora battery and pandora mem stick?
5. are those pandora tools can make it easily to play downloaded games?
6. aside pandora what can i do to play downloaded games?
7. what if i remove my pandora battery and pandora mem stick, is my psp will be back to normal having its original bettery and mem stick?

please answer my questions… i super need your answers…
coz i want to buy things to be worth it…

please answer it easy to understand…

Thank you in andvance… yahoo.answers. Rock!