On the back panel of your board, there is a small, square button called the Back-to-BIOS button. If you press in this button (it will light up if power is present) and reboot the machine, it will ignore the current BIOS configuration and will boot into BIOS setup using the default BIOS configuration. Once in BIOS Setup, you can use F9 to restore all settings to their defaults and then begin your customization again.
A couple of additional comments:
- Having the mouse work in BIOS Setup has ABSOLUTELY NOTHING to do with UEFI. In fact, having a graphical BIOS Setup capability has ABSOLUTELY NOTHING to do with UEFI either!!! At one point, one of the motherboard manufacturers, as a marketing ploy, made a totally bogus claim that the two meant the same thing (or at least were closely tied together) and a lot of naive folks actually believed them. Shame on them; it's complete and utter BS. UEFI is an architecture - a framework - for implementing BIOS firmware. You can have a UEFI BIOS with a text-based, keyboard-only Setup interface and you can have a non-UEFI BIOS with a graphical, mouse-based Setup interface; the two have absolutely nothing tying them together.
- Two important parts of the UEFI specification are (1) support for booting from drives with capacities larger than 2TB and (2) support for an improved (and secured) architecture for Option ROM firmware. (i.e. BIOS add-ons that extend the capabilities and features of the BIOS; they can allow for booting from devices not supported by the BIOS or motherboard and they can add BIOS drivers - such as the Video BIOS for an add-in graphics card). The UEFI parameters you see on BIOS Setup enable support for these two things and are a necessity for large capacity drives and for add-in cards that do not support the legacy Option ROM architecture or if Secured Boot (Windows 8, 8.1 or 10) is desired.