untested vs young

untested is not a noun while young is a noun.

Word	Noun	Adjective	Verb	Adverb
untested	No	Yes	No	No
young	Yes	Yes	No	No

As adjectives, untested and young are synonyms defined as:

Other synonyms of untested include unseasoned, untried.

untested (noun)	young (noun)
	any immature animal
	young people collectively

untested (adjective)	young (adjective)
not tried or tested by experience	(used of living things especially persons) in an early period of life or development or growth
not yet proved or subjected to testing	(of crops) harvested at an early stage of development; before complete maturity
	not tried or tested by experience
	being in its early stage
	suggestive of youth; vigorous and fresh