yes.that's correct.

How's that boy?What do you think of that boy? would be better for the second one.but there are different meanings in different circumstance.It depends on how you use it.

ئوغۇل بالا -boy or young man in this sentence.

Oyyy, sorry. It is yahshiMu, not yahshinu.

Yahshinu siz! Yes, your translation is correct)