A is an article.
No, it is not a conjunction. It is an adverb, a conjunctive adverb, used along with a semicolon to connect clauses (instead of a conjunction).
"Necessarily" is not a conjunction; it is an adverb.
No, "but" is not an adverb. It is a conjunction, specifically a coordinator (also known as a coordinating conjunction).
No, it is not a conjunction. It is an adverb.
No, it is not an adverb. It is a conjunction, and more rarely a noun.
No, it is a proposition.
It is not an adverb. It is a subordinating conjunction.
No, "thoroughly" is not a conjunction. It is an adverb that describes the extent or degree to which something is done.
The idiomatic construction "such as" is a determiner, closer to an adjective or adverb, and not a conjunction. It means "for example."
No. It is a time connective (or an adverb) and not a conjunction.
No, it is not a conjunction. It is an adverb.
No, it is not a conjunction. It is an adverb, adjective, or preposition, and more rarely a noun or an interjection.