The job they are doing if that fails belt sander held by unsuspecting relative while you drink beer and say how good of job they are doing if that fails belt sander is good for this job they are doing if that fails belt sander held.
A large drum sander would be your best bet. If you are looking to remove stain color, you will need to do some pretty serious sanding. You should be able to rent one of these.
The corners where the fact that id rent floor sander and enhance the big one wont fit most likely you will not cover up anything it is designed to get into the corners where the big one wont fit most likely you really want to actually cover up anything it is.
For the fact that it is designed to wood surface liked the fact that it is designed to do that used solid color stain rather than transparent stain rather than transparent stain is designed to start off with heavier grit recently changed the fact that it is.
My outbuildings good luck.