[Q] Inputing demon when opponent activates SA

So a lot of time I’ll score a knock down with 2 full bars, throw out some normal too early to whiff and buffer demon inside to hit them on wakeup as a bait when they try and counter.

But just as often the opponent does a SA and the ‘flash’ when their SA starts up freezes the game for a couple frames (or so it seems to me anyways).

So my question is, do I have to stop inputing my demon the moment they start their SA and try and resume in the frame or so before I get hit, or restart all the inputs to counter it in that same time. Or am I just owned?

So, you want to know how to finish demon motion, so you can maybe grab him or maybe be hit by opponent SA (depending on SA, distance, etc…)?
What about this solution? Block and punish (with demon)?

lol.

A reversal demon would lose against pretty much all supers, so yes, in any situation you will rather want to block it and then input it during the blockstun of the last hit.
Normally you want to restart inputs after your opponent’s SA, it’s dubitable that you have the immense reaction to know which directions you pressed before the opposing SA was activated.

Actually demon has a very short period of invincibility frames during the flash. So if you had the reactions it would work, though tbh it would be better to just block and punish.

parry the last hit and input the demon inside it.

Why? You’re probably just gonna jab opponent, except if you ‘true kara demon’ him.
Block, then, punish.

But this might be useful. For example, in SFIV Akuma’s blocked sweep is punishable by Chun’s Ultra 1, but Akuma can cancel the sweep into Ultra 1 to punish her

Could this be viable in 3S? Purposely putting out a punishable blocked normal to bait a SA to Demon it?

Yes it is possible in 3s to save your punishable moves with a demon. However this tactic is rarely used because unlike SF4 demon in 3s grabs in 1 frame, so you can actually apply it offensively with demon setups that will grab the opponent. (kara demon, dash demon, AA demon)