You wrote: "....create a folder Garmin and in it a folder 2087 and in it create a file update.txt ....". That won't work as it's missing the folder named "Updater" - you need this arrangement:
SD:\Garmin\Updater\2087
In the 2087 folder place the boot.bin extracted from the firmware GCD by RGN_Tool then renamed to Ldr.bin, along with the update.txt file. Read this again: [Only registered and activated users can see links. ]. You must take great care making SD flash kits, some mistakes can kill a device, like flashing with the wrong Ldr.bin for example.

It's a different method than using individual BIN files, like for patching, but similar. The point is that you could do this fw upgrade with individual .bin files too, but you need to delete any existing GCD from the device first with command "del,0:/.System/gupdate.gcd", and so if it's your intent to patch the device's fw to use unlocked maps then you may as well just use the patched BIN method with the delete command and forget about flashing gupdate.gcd. We can't give you any specific help in this forum with patching of course due to the rules here.

I note that you don't have "reboot" as the final command in that Notepad screenshot of update.txt. If you don't include it the device won't boot after flashing and it'll just stick on loader message until forced off. Also if you copy/pasted the command from my post ensure you don't have any extraneous end space or carriage return in the command.