Can I activate Windows 10 with a Win8 key?

Question

System administration

I met on the Toaster in the answers the statement that Win10 can now be installed clean and activated with valid keys from Win 7, 8 or 8.1 - she began to accept them.
It took to reinstall the system on a working computer, I decided to do so. The computer has a small 60G SSD - I didn’t want to occupy it with two systems and waste time on 2 Windows. The result is negative.
"You have Windows 10 Pro installed. The product key entered is not suitable for activating this edition"
Keys - for Win 7 Professional, 8 and 8.1 Pro officially received by the company through OLP.
Please comment on the situation.

Answer 1

I talked to MS technical support about this, and I recommend it to you: in the online chat format, the issue was resolved in 15 minutes.
The problem was similar: the laptop had 8.1 (the key was sewn into the BIOS); installed ssd - immediately installed win 10 - it did not activate. The reason was - the wrong edition. It was necessary to install "windows 10 Home for one language".

Answer 2

Here, as the correct course of action, it is recommended to install Win7 / 8 (8.1) and upgrade to Win10. It's right. But then, for some reason, the inability to do this on a small disk clings here.
I report: I managed to do this not even on a 60 GB, but on a single-chip 24 GB SSD, originally designed for a regular HDD cache. Strange as it may seem to you, everything fits, with all the necessary software, and half to a third of the disk is free (which is a necessary condition for the normal operation of the SSD):
1. First, I upgraded to Win10 on a system installed on the HDD.
2. I removed all the garbage from there (a copy of the old OS, etc. - there is a lot of it), ensuring that the system partition fits into 24 GB. We actually managed to achieve less than 20 GB.
3. Cloned the system partition to a 24 GB SSD and made sure it worked.
4. After that, the caches, temps and swap were transferred to disk D, which remained the HDD, and installed all the necessary software. Free space on the SSD now ranges from half to a third of the volume, the OS start time from pressing ON to the appearance of the Desktop is 14...15 seconds.