(1) For an external Recovery Environment, make Win 10 Installation media here...
https://www.microsoft.com/en-us/software-download/windows10
Download Windows 10 - This is always the latest finalized Windows version, currently 20H2.
Download MediaCreationTool20H2.exe & run it to make a Windows 10 Installation USB drive or burn an .iso to DVD. Follow the instructions under "Using the tool to create installation media". As it says, match it to the Language, & Architecture (x64/64-bit or x86/32-bit) of the computer on which it will be used. The Windows Edition to take is "Windows 10", which includes both Home & Pro.
- Then, to boot it, press an F-key during boot to get to the BIOS Boot Menu. If you don't know it...
Get access to BIOS settings & Boot Menu: F-keys/Hotkeys by System Manufacturer (OEM)
Note: That is an informative 3rd-party site. But I know nothing (bad or good) of any downloads or links that are there.
(a) Insert the DVD or plug in the USB Installation media.
(b) Boot or reboot the computer.
(c) Press & hold the F-key at the manufacturer's logo (or at the black screen just before the logo).
If the key was pressed in time, mine shows activity at the bottom of the screen,
& the BIOS Boot menu soon shows up.
(d) From the BIOS Boot Menu, choose the "UEFI" option for the media, if offered.
Mine names the device brand & precedes it with "UEFI:".
(e) If it were a DVD inserted, you get a message to "Press any key" to boot it.
If not pressed in time, the DVD will be bypassed & Windows will try to boot.
(f) When the Installation media boots, select "Repair your computer" instead of to install.
The computer will reboot to the Recovery Environment at the "Choose an Option" screen.
(3) At a Command Prompt, Notepad works well to backup files...
(a) Plug in a USB drive on which to copy your files.
(b) Get to a Recovery Environment, & at the "Choose an Option" screen,
click "Troubleshoot > Advanced Options > Command Prompt".
(c) Enter Notepad at the Command Prompt.
(d) In Notepad's File menu, select Open.
(e) Set Notepad to display all file types with its requestor at bottom.
The files you want are likely in the folders at "C:\Users<your user name>". Remember to Refresh the screen after a paste. Additional notes...
o Notepad's left pane has only "Quick Access", "Libraries", & "This PC".
o Click This PC to switch from C: to the USB drive & back again.
o Double-click a drive or folder in the right pane to open it.
o Right-click a file or folder, & select Copy. That seemed instantaneous.
o Go to the USB drive, right-click in Notepad's right pane, & select Paste.
I had an hourglass for just about a minute - or was it two - for 1.3 GB.
o When the normal pointer reappears, right-click in the right pane,
& select Refresh - or I think you never will see it.