An ERM can grow back, although this is unlikely. If it does grow back, it can be peeled again. Rates of re-growth vary somewhat by surgeon--from about 1% to about 5%. Peeling the ILM and the ERM is thought to reduce the rate of re-growth.
Yes it can reoccur. Each case is unique and its not possible to give exact figures. Air and SF6 gas reabsorb, balanced salt solution is reabsorbed, silicone oil is removed surgically.
JCHMD