Microsoft started requiring Secure Boot to be enabled by manufacturers beginning with Windows 8, and Secure Boot is only available on UEFI-based motherboards. It's gotta be there somewhere in your settings. It can almost always be disabled, but I have heard of a few rare exceptions that do not allow it to be disabled. When you put the BIOS into Legacy mode you disabled Secure Boot then, but there is usually a separate setting so that Secure Boot can be disabled and UEFI mode can remain enabled. There is a long, ugly, convoluted history between UEFI and Linux, and there are still problems with some Linux distros and with some hardware.EDIT: no i dont have a secure boot option
This may be the source of the trouble you are having. GRUB is looking for a Windows bootloader, but Acronis may be shielding that. Just wild-guessing (one of my hobbies )... but I don't know how for you to proceed to make GRUB primary while Acronis is in place, unless the boot-repair tool mentioned above might work. I don't know if manually editing the GRUB config file will work either because I don't know if you can identify where your WIndows bootloader is actually being stored or accessed.EDIT2: Acronis Loader is Acronis Backup software loader that allows you to boot into its recovery console before windows launches, I guess it replaces the MBR with its own, I could revert it back to Windows but then I wont be able to restore windows if I cant log in, I dont have any DVDs or USB spare to put recovery console on.
But, in reality, you are dual-booting now. You just have to choose the Boot Menu if you want to start Linux.