[CCleaner v5.43.6522 Always Skips Internet Explorer?]

I don't know if WIN 10 has it, but if it does, try Resource Monitor. It is possible for a task to be 'finished' in the CPU but still reading/writing to disk. If so, it may take 5-10 minutes for everything to finish, especially if you have been doing some heavy-duty work using IE.

'perfmon.exe /res'

[Why the constant updating of the Program?]

From what I have seen, some file names get changed in new releases also to avoid (my guess) infection by particularly nasty viruses.

As far as registry stuff, I back up my entire machine before running CC. When done right, it can do wonders. But if you delete the wrong stuff (esp. in registry), your machine may not boot. If you don't know if something can be safely deleted, I would suggest that you DON'T delete it until you find out for sure.