>but every one does not know how to react on"sleep" command. may be those in the videos already know how to react on hypnotic commands. And they do not need pretalk.
How many people will properly understand the command "sleep" is an interesting question, but it is not the same question of whether instant inductions can work without pre-built expectancy. They can and do.
It is a misconception to think of a "pretalk" as something you do before the induction. The pretalk is the induction and the induction is merely triggering post hypnotic suggestions. Explain it all "beforehand" or do it on the fly - doesn't matter. If the only problem is that they don't understand what "sleep" means, then while they sit there confused and deer-in-headlights, tell them more specifically what to do (you know, that stuff you would have said in your "pretalk")
"Expectancy" isn't quite on the money either, as it's just a proxy for direction of attention. If you can't rely on them to direct their own attention where it needs to go based on some handy expectations, as in a cold instant induction, then you need to be really on top of your game in directing their attention where it needs to go on the fly.