Hmmm…
Let me see if I have this correct.
I assume you had all the timing marks aligned … cams, crank when you had the new belt install.
Then proceeded to turn the crank bolt, realized your mistake then kept turning the crank (without the cams turning one full revolution ( 360*) so that you could get the key installed.
If I got that correct, that means your cams are still set at TDC but your crank rotated 360*.
If you did managed to turn the crank the 360* without any type of lock up ( a piston hitting a valve ) you are EXTREMELY lucky.
Though it would be harder to tell with the spark plugs installed fighting cylinder compression.
What you would need to do is:
First, remove all the spark plugs
At this point you could try looking down each cylinder with a bore scope and look for any contact marks on the tops of the pistons for contacting the valves.
If you decide not to …
Second, Slowly and very carefully bar the engine over (by hand)
Third, Triple check your timing marks and that #1 cylinder is @ TDC both valves and piston.
If by some act of god there was no contact between any valve and piston turning the crank forward 360* you should ok.
Remember the whole engine needs to rotate 720* for all cylinders to complete their 4 strokes.
The crank repeats its position every 360*
Reinstall your plugs then cross your fingers and try to start it.