How can I strikes while moving backwards like Anderson Silva did to Forrest Griffin and what are some drills to do it
Based on the very detailed question OP has posted, my suggestion for learning how to strike while moving backwards it to learn to strike better. I mean, maybe I'm crazy, but learning to generate power from any angle (the goal of good bag/mitt work) might somehow, you know, benefit your ability to, you know, strike from any angle.
Seriously, if you really want to go out of your way to drill this specifically, then drill it on the mitts or heavy bag. Not sure what specific "drills" you're looking for. When you hit the heavy bag and it's swinging backwards, move in on it, then when it starts to come back to you, work your footwork backwards and land whatever you plan/hope to land. Or if you're working mitts with a partner, then just have them drive you backwards for (X) amount of strikes before you switch it up and toss your counters.
Good luck OP, good luck.