Spare tyre CAN be an MOT fail if its bald, but its not required.
If its bald, take it out.
If its fitted, it must work.
No no no no no wrong
No no no no right.
If its bald and you leave it in the car at test time, it can be a fail.
As its not a requirement, you can remove it.
But like I said, If its fitted, Its got to work.
I fell foul of this when I took my old Delica to one of those Council run MOT places that the ambulance and Police use.
I failed for bald spare tyre and non functioning spot lights.
Removed the spare, covered the spots, retested and passed.