I began as a mild expression of surprise.
At 2, I was a U.S. Army soldier.
At 3, a revolutionary separation expert
At 4, an Aussie child's toy
At 6, a plant with yellow flowers
At 7, more of the same
Then I slept for a few and became what?
Going hamateur was close, but not quite right.
G = "Gee" (thanks to Kingrames)
GI = US Soldier (thanks to Going hamateur)
GIN = Cotton gin separates cotton (thanks to Going hamateur)
GING = Australian slang for a slingshot
GINGER has yellow flowers
GINGERS more of the same
Final answer is:
GINGERSNAP = GINGERS plus NAP
I believe most of it is:
G": as in GEE WILLICKERS BATMAN, credit to Kingrames (I may have missed the hint) GI: Military soldier
GIN: Cotton gin helped the industrial revolution and separates cotton from seed
GINKGO: Chinese tree with yellow seeds
GINKGOS: Same deal
slept for 7 and became:
GINKGOSMNP.INC an HP command injection exploit!