Code Review: Last digit of any (reasonably large) a^b (Analytically) (4 Solutions!!)

Code Review: Last digit of any (reasonably large) a^b (Analytically)

Helpful? Please support me on Patreon: https://www.patreon.com/roelvandepaar

With thanks & praise to God, and with thanks to the many people who have made this project possible! | Content (except music & images) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing | Music: https://www.bensound.com/licensing | Images: https://stocksnap.io/license & others | With thanks to user Toby Speight (codereview.stackexchange.com/users/75307), user sato (codereview.stackexchange.com/users/235420), user ruohola (codereview.stackexchange.com/users/199968), user Peilonrayz (codereview.stackexchange.com/users/42401), user N3buchadnezzar (codereview.stackexchange.com/users/61495), user Ilmari Karonen (codereview.stackexchange.com/users/9012), and the Stack Exchange Network (codereview.stackexchange.com/questions/263312). Trademarks are property of their respective owners. Disclaimer: All information is provided "AS IS" without warranty of any kind. You are responsible for your own actions. Please contact me if anything is amiss at Roel D.OT VandePaar A.T gmail.com