Ghypu

You have to restart. From my knowledge, the updated files aren't compatible with older saves. Does not work for pokemmo

From my experience, the TM is used if the pokemon you are using it on, did not have 4 moves learned already.

Only a fellow player so I can only realistically answer the 3rd question. You shouldn't randomize as it does cause issues. There are tons of extra pokes at every place you can encounter so it shouldn't be a problem