i used to do aikido for a few years. i can't recall the names anymore as this was close to 20yrs ago, some things we did i wonder if they are allowed in mma? i've seen arm bars and leg locks by mma fighters work to great effect in matches. i remember one hold we learnt which involved the opponents hand and it was excruciatingly painful if done properly. obviously it's basically just twisting and pushing the hand towards the opponent. i don't recall seeing this kind of thing in the matches i've watched, maybe i've not watched the right fights where stuff like this has been applied? i ask this as i believe these type of holds[involving the hand], would get a submission quite easily. also, is a fighter allowed to bend an opponents fingers back? can a fighter strike the other person on the back at all?
Small joint manipulation is illegal in MMA. Strikes to the spine or back of the head is illegal in MMA. (For obscenely obvious reasons) And, while the overwhelming majority of what you're talking about falls into "small joint manipulation", the one's that don't, such as manipulation of the wrist, which is often used by paramedics and such, simply don't work even remotely well, if at all, in a fight. Enjoy the fights, sir.