Let’s just say I have all the units required and all the GEs and prerequisites completed in one year at a community college, is it possible to apply as a junior to a UC? Also if I were to not get accepted, would it be possible to apply again the following year?
Sophomore / junior standing is met by reaching a certain amount of transferable credits. If you have completed two years (about 60 credits) of transferable coursework in a year, you can apply as a rising junior.
As far as I know, you can apply the following year, if rejected.
Best of luck!
Just the answer I was looking for… thank you so much. If anyone else has more info feel free to share. 
Just a note about applying again if rejected. Your chances will most likely not change, if you reapply. Reaching that 60 credit threshold means you can’t improve academically.
Between now and applying a year later, the only thing you can do is perhaps improve your EC’s (though that won’t boost your chances by much, unless your EC’s were really weak), and improve your SAT / ACT score (but by that point scores aren’t going to mean too much).