With a .22 revolver, you can shoot one firearm in multiple categories, even if it's not theoretically ideal.
For instance, with iron sights you can shoot:
Revolver (An obvious match but you compete against lots of $2000+ Freedom Arms revolvers. Not a big deal unless you worry about taking home 1st place consistently.)
Standing (Perhaps the best category, in which it's more about the shooter than the firearm.)
Production (Great for warming up/sighting in, if needed)
Unlimited
1/5 scale (A real challenge, though!)
And you can shoot the optics categories as well with iron sights, but only if you are a glutton for punishment!

With a centerfire iron sighted revolver you can not only shoot the Big Bore categories similar to those Smallbore variations above, but also Field Pistol (1/2 scale targets shot standing at Smallbore distances. Very difficult, but rewarding!)

If you like Optics on your centerfire revolver, probably the best categories in which to compete are:
Field Pistol Any Sight (100yd)
Unlimited Standing (200m)
Otherwise you are restricted to Unlimited Any Sight and 1/2 scale UAS. Some ranges also include Hunter Pistol. (There's both a Short Course and a Long Course version. 6x max magnification shot freestyle on both.)