How can I merge system and boot partitions

I do not know if further clarifications would contribute to anything, but I will give a little more information.

Info for my PC: cpu amd fx-6350, ram 16gb ddr3, video radeon rx580 8gb, 3 x 1tb hdd. I will put and screenshots of partitions and of System Reserved partition (seen through windows 7)

The next step I am considering is to clone C partition from hdd-1 to hdd-2. Dual boot – 1^st for work, 2^nd for games. And last step – full backup of both installations (bckp of 1^st on hdd-2 and bckp of 2^nd on hdd-1).

I tried something different – i did active partition C: and cloned it on hdd-2. Then I made the partition System Reserved active again. So I also got Dual-boot Windows and used EasyBCD (EasyBCD is located on the 3rd hdd) to make a startup menu with both Windows, but loading the second Windows is very slow and goes through restarting the computer (loading the first Windows is fast and does not go through restarting the computer) - bottom video link.



Here's slow loading cloned Windows
YouTube

Steve C said:

Is this action wise to avoid future upgrade problems?

No, it is not wise to do. The OP only asked how to do it.

Kyhi said:

.... To Fix...
Set OS2 Partition Inactive
Open RUN and type MSCONFIG
goto Boot Tab > remove any Entry - Not related to C:\
open command prompt(admin) type > bcdboot D:\Windows

reboot and you should have two OS boot options -
Use EasyBCD to rename one OS = Windows10 Work
thus you can differentiate between the 2

I tried this, but the issue I talk about (seen on the video) still exist – if I choose 1^st OS in the menu (no matter which one I put first), this OS immediately starts loading, but if I choose 2^nd OS, then computer first restart and (after a little delay) begin loading. I guess it happens because these two OS's are on separate hdd's, initially BIOS configured as bootable hdd with the first OS in the menu, but when I select the second OS, it is on the second hdd and so BIOS should put this hdd as bootable and therefore the computer restarts. But I don't understand why first appears Windows 10 logo (and something loads in the background) and only then the selection menu pops up.
One more thing - if the hdd-1 is damaged, will the menu reappear when the computer starts (so I can choose the OS from the 2nd hdd)? Or to put it a little differently - if both OS's are independent and each is on the first active partition of the two hdd's - will this make the menu appear so I can choose the other OS?

If I remove System Partition, can I have problems with updates to next Windows 10 version?

render1967 said:

If I remove System Partition, can I have problems with updates to next Windows 10 version?

Yep. It could complain that your disk is not in a standard layout.

Kyhi said:

....
As a test (to answer your own question) unplug First HDD and see if the second one Boots...

I tried this - computer stuck after POST.

Later I make backup of 1st OS, format OS2 partition and restore backup of OS1 there - 2nd OS does not boot.
Remove entry for 2nd OS in MSCONFIG, add entry via cmd prompt, but after restart don't want to boot in 2nd OS

Thank you all for your answers!
I've tried different options and think I've found the only convenient solution for me (if I can call it that). Two independent installations of Windows 10 on two separate hard drives and the choice of boot disk via F11 when booting the computer (with additional BIOS setup for 10 seconds hold of screen, from which I can press F11).
That way, even if one of the hard drives gets damaged, I'll have a fully functioning computer.

You can set up dual booting of two different hard drives with the Windows boot menu. Lot more convenient then going through the BIOS boot menu options every time you want to switch, IMHO.