Hey all new to this forum. I did a timing chain DIY with a friend's honda accord euro 2010 LX with the K24Z3 engine (we did it together) and the valves were damaged after he cranked the motor a couple times. We made absolutely sure the timing chain was timed with the timing marks on both cams and the crankshaft at TDC positions on the gold links while using cam locking pins. And the chain tensioner was set about 3-5 clicks after we let the pin out. We spun the crank a couple times clockwise with little resistance. And we also made sure we put everything back together as it were before like the belt, pulleys, rocker cover etc. The diagnosis of the bent valve was determined by my friend's local mechanic which I would assume he did a compression test of all 4 cylinders.

What could have caused the valves to be bent?
Did the valves hit the pistons? If so did we miss a crucial step when doing the timing chain?
Did we need to have done a valve lash adjustment after doing a timing chain?
Is there more potential damage than just the heads?
Does the lower block need to be pulled apart and inspected as well?

Any help would be greatly appreciated and if someone could shed some light on where we went wrong with this DIY. Thanks!