How to restore courses from a lower version Moodle

Dear Ken,
I likely use the migration method. The backup / restore courses across the Moodle versions causes the fact that the quiz does not work probably although I just have conventional Multichoice questions (available in both version) in that quiz.
Another thing I would like to ask you is that whether the upgrading process does modify somethings in the moodle_data ? Can I just run a "transient" moodle instance, having 3.11 DB and 3.11 code but with a dummy moodle_data, then I perform the upgrading process to 4.x, and finally if everything goes well: I see users, courses' structure,... I can clone the 3.11 moodle_data for the upgraded moodle instance.
You can ask why I don't just clone it BEFORE running the upgrading process . Of course I have to backup the current system, but the simple/fast backup/restore is to clone the DB and the moodle_data (and of course the code). In my case, DB ~ 300GB and Moodle_data takes about 600GB or more. So I think I can save the space / time in case something goes wrong (cloning 600GB then cleaning up that 600GB, also I need 600GB space more). But if the upgrading process needs modifying also the moodle_data, it is inevitable to clone it before upgrading.
Thanks for your advices
Son