So the issue you are facing was from not quite disclosing exactly what you needed and why. I am going to go out on a limb here and say you got a used vita with a previous owner's PSN name, or you lost the information to the prior account.

Might be a bit of a pain in the butt, but changing account doesn't change the registered account ID on the apps you have installed, or on the memorycard, nor does it 'unhack' a vita. For the SD2vita, if you can access the card on your PC, you can delete the id.dat and it should let you use the memorycard in your vita again. For the apps, the 'easiest' solution would be to accept loss of saves on games and start over by re-downloading them, but a vita save manager could be used to retrieve them and separate them from the previous ID I would think. That said, any trophies you earned previously won't pop upon booting the games up, you will have to re-earn/flag them. As a note, Adrenaline may still behave like its linked to a previous account, but as PSP and PS1 games don't have trophies and are stored in somewhat plain view, its easy to back up these saves to a PC or even just elsewhere on the SD2vita, so assuming you don't have any issues reinstalling Adrenaline, that should be a non-issue. The same can be said for retroarch.

Though in most cases, all of these things to purge the previous ID from apps may not be entirely necessary if you don't care about one extra step to boot things or trophies. By default, it should tell you 'you can't earn trophies in this app' when booting them up with a different account with an 'okay / cancel' pair of buttons at the bottom that you can click past.

At least, thats how I interpret your issue, and my proposed solutions.