Why would you want to do it? Both PC come with win 10 already installed, its better to just move your data from old to new
Win 10 on Lenovo PC is a special version, it only works on Lenovo. This is a pretty unique case though as you moving it from 1 lenovo to another, not sure what would happen. There would likely be activation issues with win 10
I think this depends on how simplistic a job you are talking about. I would say that on a simple level, you are unlikely to just get it to work by just taking the drive out and putting it in the new computer.
I cannot vouch for these people and I do not know if they are safe or if it really is "free" like they say. When it comes down to it though, the answer to your question is that it is not just a straightforward swap.
Take for example when you reinstall windows 10. You don't need the key. It auto-detects your system. I have just done it recently. I was a bit reluctant about re-installing but it worked out fine in the end. The fact that I didn't need to do anything other than just reinstall and wait for it to activate it is a good indication of how hardware dependent it is.
At a calculated (and reasonably experienced) guess you can pretty much change anything but the motherboard, CPU or the hard drive that the Windows OS was installed on. Change RAM/ other hard drives/ GPUs etc to your hearts content.
On Transferring a System Drive with Windows 10 to a Completely Different Machine
Yes, you can do this, but you will get one of three results:
1. The machine will not boot, period. In which case you will simply have to do a completely clean install of Windows 10 anyway. If the hardware is really different this is the most likely outcome.
2. The machine will boot and run, even relatively well, and you can reactivate Windows, but because the hardware is completely different you will spend weeks to months chasing one issue after another because virtually nothing from the old hardware matches the new and that would make any OS crazy. It’s expecting things that just aren’t there anymore.
3. The machine will boot and run flawlessly, though Windows will not be activated. This happens, but is the least likely outcome. I’ve personally never seen this occur, but there are enough credible reports that it must happen on occasion. I would also imagine this only happens when one is dealing with actual or virtual "hardware twins" for the transplant.
My general advice is to start again from scratch. It all depends on what your tolerance for experimentation and frustration is.
If the machine in question ever had Windows 10 installed and activated at any point in the past it when you reinstall it will automatically fetch the digital license for the edition that it knows that machine last had. You can, of course, choose to upgrade it to a different edition, e.g., Home to Pro, by purchasing a Pro license key and using Settings, Update & Security, Activation Pane, Change product key link. After doing the under the hood activation for the components that were previously locked, you’ll have Windows 10 Pro instead. Windows 10 does not have to be reinstalled, as all components are already present, it is the license key that determines which are unlocked and active, which in turn is what determines the edition you’re running.