What would the yeild look like if I were to go 12/12 with a 4 inch tall plant that...

that just got its first set of full grown leaves? This is bagseed and I'm doing it to make a smoking stash, I have 4 plants. After this yeild is done I'm going to buy real seeds so if I harvest quickly this time it would probably be better, the question is would I have enough yield from say 2 female plants that started on 12/12 very early to smoke like half a gram a day for a month or two?

Probably not. Your plants is only 4 inches tall but with probably only 4 nodes. If you 12/12 you MIGHT get a couple grams per plant. Also dont forget their not guarentteed female so :/. If you want a quick grow I would veg for atleast 2 weeks, up to 4 weeks, then flowering.