It is usually a preposition, though it is sometimes a conjunction.

Both...and is a correlative conjunction. It is used to connect two equal grammatical elements together in a sentence.

The grammatical conjunction in this sentence is and. A conjunction is used to connect phrases, sentences, clauses, or words. A conjunction is typically one word but there are a few short phrases that also serve as conjunctions.

No, "nor" is a coordinating conjunction used to connect two negative ideas in a sentence. It is often used in parallel structures to join phrases or clauses that have similar grammatical forms.

No, "none" is not a coordinating conjunction. It is a pronoun that means not any or no one. Coordinating conjunctions include words like "and," "but," and "or," which are used to connect words, phrases, or clauses of equal grammatical importance.