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#101
I don't know the differences between them as I never used Classic Shell. I used an alternative in the past. Lots of users say that Classic Shell works fine for them.
It's stated that Classic Shell is no longer developed/ updated and Open Shell is a fork of it which is maintained.
There's a decent enough review here:
Open-Shell - Classic Shell Reborn, and pretty neat too
One feature i like is the ability to display Windows 10 Start Menu if you need it for some reason.
Classic Start Menu, Classic IE and Classic Explorer.
There is more info if you right click Start. Then choose Help.