arcadekidflo wrote:1. I want to update it to 3.18 , can i do this or it only updates to the latest firmware ?
Yes, you can manually update the Vita to FW 3.18.
viewtopic.php?f=65&t=23013
arcadekidflo wrote:2. I also have a PS3 , i could download an exploitable game but which one to get and how do i put the same account on Vita without accesing PS Store ?
Best exploit games for 3.18:
http://wololo.net/2014/09/17/fw-3-18-ex ... e-you-can/
Link the Vita with your PSN account:
http://wololo.net/2013/04/17/lower-ps-v ... r-dummies/
arcadekidflo wrote:3.What game should i get to enable PSP mode ?
See the answer for your second question.
arcadekidflo wrote:4.What about installing Vita demo PKG , what is latest fw where it works ?
The Package Installer definitely works on FW 3.18. (it also works on FW 3.50, but the way how to run it on firmwares >3.18 hasn't been released yet afaik)