sometime vs former

sometime is not a noun while former is a noun.

Word	Noun	Adjective	Verb	Adverb
sometime	No	Yes	No	Yes
former	Yes	Yes	No	No

As adjectives, sometime and former are synonyms defined as:

Other synonyms of sometime include erstwhile, old, one-time, onetime, quondam.

sometime (noun)	former (noun)
	the first of two or the first mentioned of two

sometime (adjective)	former (adjective)
belonging to some prior time	referring to the first of two things or persons mentioned (or the earlier one or ones of several)
	belonging to the distant past
	belonging to some prior time
	(used especially of persons) of the immediate past

sometime (adverb)	former (adverb)
at some indefinite or unstated time