I am looking to build a 2 story garage and want to know if my framing will support the concrete. Garage is 28x36. In the middle of the 28 width there will be a steel beam w/columns underneath for support. My question is can I frame the subfloor w/2x12x14' (1/2 of 28' span) 12 on center and will it support 4" of concrete on second floor? Subfloor framing will be covered with 3/4 advantec then 1 1/2 styrofoam (for insulation). A good friend of mine did his garage the same way approx. 10 years ago without problems but his is 2x12x12 16" on center.

Curious as to why a concrete floor ?

Be smart. Get an engineer to calculate supports, amount and design of reinforcing bar and thickness of concrete floor.

with an L/360 deflection, and using 120 psf combined live and dead loading, I get a maximum span for 2&btr spf 2x12@12" oc of 13'4".
Your concrete topping s/b approx 40-50 psf unless you can get a light weight topping mix, and that leaves 80 pounds, of which 60 can be live, and an additional 20 for dead. These loadings are light for storage, and are more inline with housing flooring.

It would be best of you can pour 1.5" topping instead, which is what most people do. You can frame your walls, and then pump in a 1.5" Lafarge mix called Agilia and self level it to the top of the bottom plate, or traditional concrete with small aggregate, or light weight aggregate concrete of course (ideal).