Hidden information about the current firmware installed on PSVita can be revealed by following the following steps:
1- Go to Settings > System > System Information
2- Press simultaneously R Trigger + L Trigger + DPad Left + Square for a few seconds
3- Release those buttons then immediately press the Start button
This menu contains information about system build, repository, revision
It has been reported that the exact combination of keys works on PS3 as well, also accessing a similar hidden menu, and also on PSP if you keep holding Start after the first buttons combination (credit to Foxi4).
1- Go to Settings > System > System Information
2- Press simultaneously R Trigger + L Trigger + DPad Left + Square for a few seconds
3- Release those buttons then immediately press the Start button
This menu contains information about system build, repository, revision
It has been reported that the exact combination of keys works on PS3 as well, also accessing a similar hidden menu, and also on PSP if you keep holding Start after the first buttons combination (credit to Foxi4).