1. old games i.e games released before 3.50 OFW were designed to run at 222 MHZ ...... They can also run at 333 MHZ
2. No ....... Actually sony with its 3.50 & above firwmware unlocked the 333MHZ speed,.... & New games can utilize that speed
3.Nop....... Games designed to run at 222 MHZ can run on 333 MHZ ....... And in some games you can see some increase in performance.... Like in GTA
4. Yep battery drains quite a bit when running at full speed
P.S :- Here's a link to a video showing difference between 222 MHZ & 333 MHZ in previous build & final build of GOD OF WAR : CHAINS OF OLYMPUS .....
Gametrailers.com - GOW PSP 222 mhz VS. 333 mhz by Adrian007