Stocks are suspended to the Grey Market every day, and stocks come off the Grey Market, every day, that's a fact!
No, it is not. It is in fact very hard to get off the Greys, as the EMGE case illustrates. A literal handful of companies have managed it over the past five years.
And before you cite venue changes from OTCMarkets, be aware that pretty much all OTC companies begin as Greys. They're assigned that status while they're waiting for FINRA to approve their Form 211.