Cannot install RW_LEGACY and cannot BOOT

I want to boot Tails and others, and I followed these instructions: https://www.reddit.com/r/tails/comments/pd56ha/cheap_chromebook_for_tails_setup_guide/

I reached to enter the codes:

crossystem dev_boot_usb=1

crossystem dev_boot_legacy=1

crossystem dev_boot_altfw=1

After it, I tried to boot my Tails pressing Ctrl-L but it says

Press a numeric key to select an alternate bootloader:

`2 TianoCore TianoCore bootloader’

I press that number but nothing happens.

After it, I read in answers that the solution is to use RW_LEGACY to have dual boot.
I followed the instructions from MrChromebox: https://www.reddit.com/r/tails/wiki/faq/#wiki_can_i_run_tails_on_a_chromebook

But in the installation of RW_LEGACY it says that

"Install/Update RW_LEGACY Firmware (AltFw / edk2)

NOTE: RW_LEGACY firmware cannot be used to run Windows. Period.
If you are looking to run Windows, see the documentation on coolstar.org.
MrChromebox does not provide any support for running Windows.

Press Y to continue or any other key to return to the main menu. "

Here is the dead point where I am. I don’t know why I cannot install it, if my device supports it.

Thanks you if can help me.

My device is MIMROCK. In the website says it’s supported: Supported Devices | MrChromebox.tech
When I press Ctrl-L

Press Y then hit enter to continue, like the script says?