I've checked setupact, msinfo32 and both methods say that I don't have UEFI
Correct, which is what I said in my last post. You do have a FAT 32 partition on sdc1 and that drive seems to have an attempt at installing a Linux system so you apparently tried to install Debian UEFI which I would not expect to work. Your windows is installed MBR.
I'd suggest you delete everything on the test drive (sdc) and re-install whichever system you want and make sure you select the manual method to install. With any Ubuntu it is called Something Else. This gives you more options and more control You need to select the Device for bootloader installation and if you are installing on sdc, that would be /dev/sdc. The default is /dev/sda which you did not select in any of your installs since there is no Grub boot code in the MBR of that drive.
I see in your last post you installed Ubuntu successfully, correct. You've overwritten it obviously as the only Linux partitions are on sdc which you indicate is the failed Debian install. I have no idea what "Apricity" is so can't comment on that.
The link below has an excellent and detailed tutorial on installing Linux in dual boot and also a lot of other useful information.
In regard to UEFI, you might take a look at the link below, particularly the section under General Principles which should apply to other systems than Ubuntu.