The word ‘discuss’ should be used without the preposition ‘about’. It seems to me that ESL students tend to mistakenly use ‘discuss about’ mainly because we do say ‘talk about’.
I see nothing wrong with saying “Wait!” but your description does sound as though “Stop!” might be more (or at least just as) appropriate.
I’d use “Wait up” informally, for example, if I wanted some friends to stop walking temporarily so that I could catch up with them (i.e. so that we could all continue walking together).
“Hold on” can be used in a variety of situations to ask someone to pause or wait. You often hear this in telephoning situations, for example. To me, ‘Hold on’ often has the sense of ‘Please wait while I do something else’.
Oh I am getting so interested in this talking! I began to see the light at the end of a tunnel with:
But I’d like to ask a further question on the first example. Is it possible or not to consider the verb see carrying both an object and an objective complement so that the sentence could also be described as: I see nothing (as) wrong with … or I see nothing (as a) wrong (thing) with … ?