NEEDS to do a cylinder leakage test... Said about that didnt I when we were at yours, all the rockers and bits went back on properly...

When I did the stem seals the engine had already previously had belt removed by you IIRC, I took all the rockers off the head at the same time then changed the seals as you saw, I then fitted your new belt and is DEFO 100% timed up correctly as has been confirmed by a couple of people as we double checked this when it wouldnt run

I would suggest between the time you took the belt off and I took the rockers off, the bottom end has been turned over by the crank causing valve damage

as you know it was running fine before you took it out the previous car and as you say its a brand new short engine which has only done 20oddK on std power

NO WAY its worn bores or rings especially while sitting on the garage floor lol

I would suggest the rust in bores is a little far fetched, I imagine the reason it looks different is because number 4 is firing, the rest are caked in petrol etc, and viewing it through the boroscope is emphasising this... BUT this still doesnt explain why it DID run..... since its been in your car...

Do a cylinder leakage test before removing head IMO