At 1:42-43 Hazama did 3C and canceled into the stance which can go low, go high, cancel, or flash kick. In this situation if you know they will do the stance you should always do 3C on reaction to the stance. 3C will hit Hazama out of the air if he does the over head attack, will be fast enough to beat out the low attack, will whiff the flash kick (but you recover fast enough to 214A him), and if he does the cancel it will not be fast enough to avoid being hit by 3C.
When you hit Hazama out of his overhead hop with 3C it hits him in the air so he isn't grounded so 2B can't follow up. I did 2B there just as a habit as a follow up to 3C.
Also if Hazama doesn't cancel 3C into anything doing 3C will hit him before he recovers.
Of course doing 3C against Hazama's 3C isn't always the best idea because if he knows you are doing this he can cancel into his 236D fireball which will beat out Hakumen's 3C. However, he can't follow up on CH 236D on less he has you in the corner or RCs.
Oh the 2As in most of the situations were to give me time to think about what to follow up with, either to renka combo, go for a mixup, or watching for bursts. You really shouldn't do renka if you can't follow it up with a combo, but I hate not being able to get knock down from 2A. But, that's just a bad habit of mine.