Oh that's easy to do. You don't need norms or average rating or anything. You just have to win a tournament; what is it World Senior Open or somesuch? Help me out here folks...
can i become a grandmaster if i start at 92

Lol , what an amusing predicament. Best of luck to you sir. "Better late than never, but never late is better" -Drake

As long as you become a SuperGM by the age of 70, I reckon by the time you are 92 you can become a GM...

Sure you can become grandfather at age 92
If he didn't start on the path to grandfatherness ages ago, the title will elude him.
i would appreciate feedback