That cylinder should clean up fine. OEM cylinder kits are NLA glad you're cleaning it up. Make sure you get ALL the aluminum transfer off. Hit it with some wet/dry with dish detergent.
If you are not sure if it's transfer you could dab it with some acid being careful not to get any on any defects or port edges, I use a q-tip. If it's transfer it will react/dissolve/bubble with the acid then wipe off. Have rinse water and baking soda solution (to neutralize acid) handy.
I think you meant carbon at top of cylinder? Yes, clean that out. Some copper Chore Boy is good for that.
The bad scoring is on the clutch side where things get the hottest first. Find out what caused it so it don't happen again. Since it pressure tested O.K. it's either a carb setting too lean or bad mix. If you are sure of the mix, Hi carb setting was too lean and the long cut in the big oak it got too hot (see Okie's post #19). That's assuming the flywheel housing and cylinder fins were not caked up in sawdust crud.
Post some more pictures when you work on the cylinder some more. I'd get a OEM piston if money is not tight but Meteor will do too (< 1/2 cost of Stihl). I think OEM pistons are still available but don't have a 2022 price list to check.
