No. Sounding like something from a circus marquee, it has no subject and no verb.
The correct grammar for this sentence is: When did your friend come?
Yes, this sentence is correct grammar.
Yes, that is correct. But there should not be an article("a") before "correct".
No this is incorrect grammar. To make the sentence grammatically correct you should say: One of my cousins came yesterday.
The proper grammar is "There has come a time." "There" is the subject of the sentence and is singular, hence the correct verb form to use is "has" instead of "have."
It is more birthdays to come. There is no apostrophe.
The correct sentence is 'I will come home at 3pm'.
The correct grammar is 'did not come.' Came is the indicative past tense..come
No, the sentence "Come here once" does not violate any rules of grammar. It is a complete sentence with a subject ("you" understood) and a verb ("come") that expresses a complete thought.
'Did she came...' is incorrect. 'Did she come...' is correct.
Yes, the sentence is correct. The implied subject of the sentence is you."You come...""You enter..."
"Few days to go June will be ended soon" is not correct grammar. The correct grammar is "June will end in a few days to come." or "A few days to go until June ends."