Timing belt change issue

[Junior92]

Hi all, need some advice as I think I have made things worse. Was happy about getting the mb6 back out on the road after being stood for years. Long story short, car started up fine with jump start and I took it for a run for 10 miles and all seemed good, no funny noises from engine. I thought I'd give it an oil and filter change so started the car and let it run for 10 mins then gave it a gentle rev, heard a weird squealing noise from the timing belt area which found to be the timing belt rubbed against the plastic cover and shredded into millions of pieces. Checked the timing marks and all seemed good, belt did not jump which was a relief. Problem started when I fitted new belt as I forgot to put spring on tensioner, and I rotated the crank counter clockwise 3 times as stated in the manual not realising that the crank had jumped two teeth from tdc. I put everything back together then started the car, it did struggle to start and when it start, the engine was knocking, I must've let it started for about 10 seconds then turned it off as I knew something was not right. This is when I realised that the timing belt was put wrong by myself.

 

So now I'm worried whether I have caused any damage, like bent valves or even damaged piston. I don't have a clue how to take the head off myself but I was told I can take the spark plugs out and rotate the crank manually to see if there is any knock/slap noise but I'm not certain is this is quite the way to tell for a bent/damaged valve or piston.

 

I'm still learning these engines but now I'm s**tting myself, I made things worse :(

[noodels]

Time it up correctly and do a compression test.