Could Eri restore the One for All quirk to All Might? Supposedly, Eri has a quirk, Rewind, that allows her to rewind an individual's body to a previous state. She used this, for example, to undo the damage Izuku did to his own body when he used One for All at 100%. Could Eri restore the One for All quirk to All Might and also cure him from his injuries done by All for One? Or are there any obstacles for something like this to happen?
That's a highly speculated topic in the fan base. Since we don't know much about both quirks, we can only judge from what we know. 


Since Eri was able to restore wounds on Izuku, we can say that she can restore All Might's wound too. Eri can even rewind someone to their non-existence which, of course, means death. 
We know that quirk bullets can make a person quirkless. It's also important to note that these bullets only change your quirk status, not the whole body. 


Thus, you can assume that with experiments or by risking All Might, Eri can reverse him to a previous state where he is at his "might". 

Now, these are my own thoughts. I think Eri can reverse All Might's quirk because of how One for All works. If a One for All user passes the quirk to someone else, what's left are just the embers. So, I think she can only restore those embers but not his power. 

Eri's quirk is the most broken quirk we ever know. I think the mangaka knows this too so he won't use her because of this. It can destroy every buildup the manga has ever done.