Upgrading from 3.4.2 to 3.5.2

It will keep your preferences and shortcuts.
It will possibly modify them though, so that's something to backup in case ypou want to revert

Under normal circumstances, you need to do nothing but do the update. And even if you decide for whatever odd reason you wish to revert, no special steps would normally be needed.

But FWIW, at this point you might consider just waiting a few days (?) for 3.6. That's a more significant update, although again, no special steps should be required other than just doing it.