That sentence is grammatically correct.
The grammar in the question is correct.
That's not incorrect, but "Who are those who leave" would be better.
The correct form is Robert and I. Myself and Robert is incorrect.
No this is incorrect grammar. To make the sentence grammatically correct you should say: One of my cousins came yesterday.
no_____If the sentence is You do do that (meaning You are in the habit of doing that) the grammar is perfectly correct and the sentence 'does have correct grammar'.
The correct grammar for this sentence is: "When did you send it?"
There is no shortage of people in need of help.
No, Incorrect Grammar. Actual sentence is. This morning she received one dozen of red roses from her husband.
No, the example above in incorrect grammar. A correct example would be: "Have you taken a nap?"
A sentence with broken grammar is often referred to as a "grammatically incorrect" or "ungrammatical" sentence.
No.
The correct grammar is "Between you and me."