I accidentally restored a backup from a RB2011AHx2 to the RB493G and now it cycles through the boot process repeatedly. I tried the manual reset with the jumper hole several times without success.

What else can I try to recover the router?

NetInstall maybe.
https://wiki.mikrotik.com/wiki/Manual:Netinstall

I would like to do that, but it has to stop rebooting to do a netinstall