2. If you want native Vita hacks alongside PSP mode hacks, get 3.60. Any brand new Vita sans 2 new Japanese Slim colors is guaranteed to have 3.60 or lower out of the box. After that, you can use Henkaku's DNS server to update directly to 3.60 and can run Henkaku on it.
3. There are quite a few, depending on what you want to use. For Adrenaline on 3.60 (which is a full ePSP mode CFW that includes the XMB and other tweaks like new graphical filters)...
1. Really useful, thanks! A few more doubts just to understand how to start pls. I didn't get the part of 'sans 2 new Japanese Slim colors', did it mean that there are a few PS Vita models and they all should have version 3.60 or lower other than 2 models which have Japanese colors in a slim version?
2. And if I get one with version 3.60, I don't need to use that Henkaku's DNS server you mention as the console would be already in firmware 3.60, right?
3. What is the purpose of running Henkaku? ie, is it a different CFW to Adrenaline or ARK, or do you need both to be running in order to use a PSP emulator?