Answer:
No, it is not. Instantly is an adverb, a word that describes a verb or an adjective. Instantly is also a conjunction.
To make instantly a noun would be an instant. Instant is also an adjective, a word that describes a noun. Example uses:
Adverb: She instantly saw that one child had dropped his ice cream.
Conjunction: The bird flew away instantly I tried to reach out for it.
Noun: I will be there in an instant, Mom! (tap, tap, tap: Mom's foot)
Adjective: I love coffee, but not instant coffee.