My parents did not properly teach me how to do wudu and say prayers as well as do ghusal properly. My mother is a sunni and Dad a shia, so I mixed up rulings as was taught to me. I used to do sunni wudu and ghusal and pray salat the wrong way without tashud in second rak'aa. And I didnt have any proper resource and knowledge to understand rulings as i was little.

Now that when I read the proper method of doing wudu, prayer and ghusal, may i know if I have to make up for my messed up wudu, salat and ghusal for 21+ years?

As for fasting, I can't remember when I started to fast properly (maybe when I was 15), I never fasted for my missed fast as well as i did'nt know the rulings, now that I know the ruling I have roughly calculated my due fasts and am making up all of my Qadah fasts? May I know if I am doing it correctly or should I have to pay kafarah as well for missed fasts from the time I was 9 years?

As for the qadha of fasts, the least amount of fasts you are sure you have not fasted, only give qadha for them and in addition to that, you have to pay kaffara e takhir which is 750 grams of food to a poor person for each fast not kept and qadha not done before the month of Ramadan of the following year.
In regards to namaz, if you believed yourself to be Sunni then there is no qadha upto the time you believed yourself to be a Shi'a since you prayed following the Sunni method but if you thought of yourself as Shi'a, then you have to do qadha of those namaz prayed wrong