It is only correct if you are standing on top of a young person.
What are you trying to say? If you mean someone who is at their physical prime, you might say "at the peak of youth" or "at the prime of their life."
If you mean a young person who is top of their class, you might say "at the top of his or her class" or "the best of the youths."
'In the hope that' is the correct phrase.
If you are referring to this sentence, no, it does not resemble a correct phrase AT ALL.
The Vietnamese phrase 'Bao Thanh Nien' means youth protection. The phrase is referring to the youth festivals in Vietnam that promotes environmental protection.
This is not a sentence it is a phrase and as a phrase it is correct.
The correct phrase is "Off the top of their head."
That is the correct spelling of "phrase" (word group, or to use specific words).
The correct phrase is "Did they?".
Yes it's correct.
The correct phrase is "sufficient proof".
It depends on how you use the phrase: Can you provide me a copy of your CV? - correct
No, the correct phrase is veni vidi vici.
No, "ad verbatim" is not a correct phrase in Latin. The correct phrase would be "ad verbum," which means exactly, word for word.