Ok i read something about it. Normally i booted to twrp from fastboot with commands. The difference is that now i have not flashed the earlier version, but the 1206.
So i will try to flash an earlier version like 3.4.0 to take definitely, but i will boot from fastboot the TWRP-3.4.2B-1206 recovery, format all partition to flash this rom.
After first boot and configured the phone, if i understand, i boot from twrp flashed (3.4.0) to root the phone with magisk for android 11 (i read in another post to flash first magisk 11, then magisk 21.1 and after reboot to system). I hope this is the correct procedure.
Edit: i see that you have posted the links to the correct procedure, i will see. Thank you very much.