That's not incorrect, but "Who are those who leave" would be better.
The correct grammar is: "Are those correct?"
No, "them guys" is not considered correct grammar. The correct phrasing would be "those guys".
You can check the grammar, spelling, and punctuation of a sentence using Microsoft Word or Google. Simply copy and paste and either of those will give you the correct structure.
It depends on context. For example, in a conversation between two people: Person #1: Those items are not for sale. Person #2: Which are? In that context, it is understood that "Which are?" means "Which items are for sale?"
The sentence, 'Pity those who are unhappy.' is a correct sentence. The subject of the sentence is implied, the subject is 'you', the verb is 'pity'.
Yes, "To those who are Irish" is correct grammar. It is a prepositional phrase that correctly identifies a specific group of people.
I find nothing wrong, in grammar, in using the word "among" as the first word in the sentence. As in: "Among those who live in the Philippines, the largest religion is Catholic". Those, on this forum, who know better than I, may disagree ---- and, if they do, please correct me. Otherwise, I stand on what I say.
No, that is not good. One major problem is "it for you". Those words do not belong. They have the odd effect of creating a string of words that seems to be a sentence. It's a little difficult to explain. Better to say: Please [or kindly] find the attached file that you requested.
Yes, that's a correct sentence.
That question is very general and demeaning to those who do have decent or excellent grammar. However, most probably would agree that the lack of correct spelling and grammar usage can be a problem on the Internet in general.
"Are those they" is correct. "Are" is a form of the copulative verb "to be" and is not transitive. In this sentence it is linking two subjects; "them" is the accusative form of the pronoun "they," but since this sentence has no objects, it would be incorrect. Unless to object is known commodity understood by those involved in the discussion.
While there are many locations that offer standard grammar and punctuation checks, two sites are more comprehensive. Those site are Grammar Base and Sentence Checker.