Most careful speakers consider "unique" to be a superlative, and therefore not to be modified by any adverb, especially in writing. Something is either unique or it is not. However, the notion that a superlative may not be modified is a feature of Latin grammar, not English. Certainly Shakespeare was not afraid to modify his superlatives ( "most unkindest" is perhaps the best known example), and who are we to be more correct than the greatest writer in the English language?
The correct grammar is "A unique experience" because the word "unique" starts with a consonant sound. The indefinite article "a" is used before words that start with a consonant sound, while "an" is used before words that start with a vowel sound.
No, "most unique" is not correct usage. "Unique" means one of a kind, so something is either unique or it is not: there cannot be different degrees of uniqueness, and something cannot be very unique or most unique. It is not uncommon to hear people say "very unique" or "most unique", but this is not correct. They should be using "unusual" if they want to use it with "very" or "most".
Yes, it is correct grammar to say "Would you be so kind as to [do something]?" It is considered somewhat formal.
No, the correct grammar is "he and you." "Him" is used as an object pronoun, while "he" is used as a subject pronoun. So, the correct phrasing would be "he and you."
This should say, The next stop will be somewhere in Vasayas, then it will be correct grammar. Written as it is it is not on correct grammar.
No, "will be had" is not a correct grammar. The correct grammar would be "will have."
No, it is correct grammar, not a correct grammar.
The correct grammar is: "Are those correct?"
"On a train" is correct grammar.
"So few" is correct for things that may be counted.
"How are your parents" is the correct form.
The correct grammar for this sentence is: "When did you send it?"