I believe what you are seeing as a problem is not a problem. Lets try to divide this thing into several parts to make explanation more easy to digests.
We can see the timing chain is in need of replacement. This can wait but should be taken care of sooner rather than later. When the timing chain is done you will need the chain, small gear on the crankshaft, bearing in front of gear, tensioner parts. We do not normally change the large gear on the cam shaft.
The cam chain and it's gears is the connection between the crankshaft and the cam. The small nut on the tip of the cam shaft is holding the advance unit on the end of the cam shaft. The advance unit operates the ignition points. You must be careful with this small nut and not over tighten it. The small piece of thread on the end of the cam shaft can be broken.
Once the advance unit is on the end of the cam shaft and the small nut is tightened the advance unit can be rotated. It does this in operation. It is how it advances the timing which is what we want it to do. It will only rotate a certain amount and I forget what this is. It is the number of degrees that the ignition is advanced in operation. A total of 26 or 28 degrees or there abouts.
You are rotating the advance unit, not the cam shaft.
Never memorize something you can look up.