1) All modded psp must not be turned off and must stay on standby mode forever?
-only the newer psp 2k and 3k that run ta-088v3 mobo and above.
2) How many version we have for psp 2000 and psp 3000? Because i came across with these terms 'psp 2001' 'psp 3001'
-those are just region. package are the same and there is not difference.
3) Newer games require newer cfw?Means need to upgrade your cfw?
-depends..for now most games requires 5.55 and above (newer games according to some sources mention it's gonna require 6.00 and above)please buy the umd then.
4) PSP 3000 now can fully modded? Is it stable?
-semi modded i guess since it's temp (once unit is turn off, it becomes a normal psp)
5) Which one supports more multimedia features?PSP 2000 or PSP 3000?
-both units are the same dude. the only difference is psp3k has better screen and built in microphone.
depends on the game as usually. usually ofw are included in the UMD if an upgrade is required.