1) some plants show "preflowers" as early as 4 weeks into veg... others won't ever show until you put them into a 12/12 on/off light schedule
2) 24/7 lighting isn't "bad" persay, but a lot of people feel that 18/6 on/off is better because it givesthe pants a chance to rest.... both will veg your plants though
3)yellow spots can mean lots of things, pictures?
4)a good fertilizer is one that works... haha... so many people use so many different things... it really all depends... are you gonna go organic? or do you not care if you use chem. ferts? a lot of people use Fox Farms, General Hydroponics, and Advance Nutrients lines... so those are a few brands that'll do ya good...
5)two plants in one pot isn't the best idea.... especially if its a smaller container.... roots will compete for space and whatnot, and one may even choke the other out... also i've heard, that's a sure fire way to get 1 male and 1 female (don't take my word on that though)
6)seed to smoke you're looking at a minimum of about 3 1/2 months for something of some decent quality (it'll still be a bit harsh though)
cuz you're gonna need atleast 3 months to grow (that's if you do just 1 month veg and 2 months flower) and you'll need to wait another week or two before you're harvest dries to something smokeable.... in reality though you should let your bud cure in jars for atleast a month before you start tokin it