No boot from emmc on power up

Which Khadas SBC do you use?

I’m using VIM3

Which system do you use? Android, Ubuntu, OOWOW or others?

I want to run Debian 10 (Buster)

Which version of system do you use? Khadas official images, self built images, or others?

I built Buster using Fenix script (latest version) on an Ubuntu 20.04 virtual machine.
Main args: U-boot 2015.1; SD/USB target
Recorded SD card, boot from SD - worked fine.

Erased emmc with OOWOW
Used emmc-install to copy SD to emmc. In general, it works from emmc.

So here I am with few issues/questions:
My problem no1: VIM will boot only when I press 3x the Option button. When power is back (or pressing power button) → quick flashing white LED/no boot. If I “sudo reboot” → LED off/no boot. Power button will switch the board off (blue LED).
I would need the board to boot at least when power is back. How can I achieve it? Perhaps my build or emmc transfer has been wrong? Unfortunatelly some links to Khadas how-tos on installing Debian are dead now.

Problem no2: video output from VIM to my monitor (FHD) seems out of range on the monitor (such message is displayed). I have hdmi.autodetect=yes in env.txt. Display used to work on stock VIM Android and on test ubuntu boot from SD. So it can work with this VIM.

I will appreciate some guidance how I can resolve present issues.

Hi Folks,
what did I wrong or how should I normally install Debian 10 to Emmc to have it booting at power up?