1. Yes, it is possible but my personal recommendation is to copy only the files and reinstall the OP system. I also recommend reinstalling all programs.
The reason is very simple - you avoid errors and damaged programs and files being transferred to the new system, as well as old and corrupted registry data.
In addition to these, there are many other problems that can arise when cloning an old system. For example files and folders userpermissions etc.
So, if You want to get new fully functional and fully correct OP system, install it to new system, then copy Your files and install programs and You may be sure that You have got clean and correctly functioning system.
2. Yes, it is possible, but depends on Your main system what other systems will work correctly. Usually many people instal also some Linux version, but my recommendation is to use on one computer one OP system if not possible to use different hard drive for the second OP system. I do not recommend to use on the same hard drive two or more OP systems on different partitions and dual booting.
Yes, it's true, it is possible and works, but the question is - how it works. Decide yourself, what you do, but this is my recommendation.
You can clone your drive as Trotter suggested, or reinstall fresh using install media provided from Microsoft.
If you're using Windows 10, make sure you're signed into a Microsoft account in the Settings -> Updates & Security -> Activation section, and your digital license will be re-applied, so your OS will be activated.
If you're not using Windows 10, then you'll need to make sure that you have your product key available to re-enter during reinstall.