I would like to clarify @Dr Atul G- LNG.

You mentioned - "No—if you’ve already started the upgrade, you cannot change the user. Otherwise, yes, you can."

which means if I had not started the upgrade, I could have switched the user roles, which is not the case and I responded.

What is my option left over here?

Reset/ Wipe the instance? That might fix the issue, BUT BEFORE THAT...

Once the upgrade is OVER, I should check if it is THEN POSSIBLE to switch the user roles.

If yes, I can skip resetting the instance,

OR ELSE

FINALLY RESET THE INSTANCE!

Hope I have clarified.

Regards,

Anish