If you hit the F12 key during boot, does your BIOS give you a boot menu?
With UEFI systems, the booting is normally by system name rather than by disk. On my desktop, the system names available are “Windows Boot Manager” and “opensuse-secureboot”, with the latter as the default.
I’m suspecting that you main problem is that you are unfamiliar with UEFI booting and how it is different. If your system is using “grub2-efi” then you probably set it up correctly for UEFI.
If your BIOS has a setting to choose between legacy booting and UEFI booting, then make sure that it is in UEFI mode.
No that is not the boot menu… It can be different so you need to read the manual for your machine. but it is more like F10 or F12. We have to assume that this machine has a EFI BIOS unless told differently.
F2 is just the BIOS setup stuff not the boot selection menu.