Yes, it's fine.
All it needs is a question mark. Have you had lunch? That is grammatically correct.
It all depends on the context surrounding it, but in and of itself "please see attached letter" is correct.
yes
No, I sould suggest "What do you all expect?"
No not at all
yup...
No, the phrase "of which we are all" is not grammatically correct. It would be better to say "of which we all are" or simply "which we all are."
"Soon, you will have forgotten him" and "You will soon have forgotten him" are both grammatically correct; however, while the first sounds better, neither sounds very natural. A better phrasing, if it fits the context, would be "You will soon forget him." Alternatively, you could keep the motherly tone by saying "Soon enough, you will have forgotten (all) about him," or a variation of the like.
Short answer : Yes and not impolite at all, as suggested below. This is to be handled by you grammatically correct? requires inverted commas to be correct. It should be written as: "Is this sentence "This is to be handled by you." grammatically correct?" The sentence is correct but not very polite; it would be simpler to say "You are to handle this"
It certainly can be correct. As with all grammar it depends on how it is used
Only in the south.
Grammatically, yes.