In FFVII, when the final boss is defeated, can I return to the world map?
Solution 1:
Once you defeat the final boss, the ending FMVs and credits start to roll and eventually brings you to a screen with a never-ending pattern of stars. There's no way to get back to your playthrough - or even the main menu - without resetting the console.
So in short, yes, you remember correctly - get all the side quests completed before taking the last boss on.