#1
I've noticed this from the start, that when I go from falsetto to normal or vice-versa that my voice will sometimes crack because the air isn't circulating properly. Is this bad? I'm not feeling any strain, just that sometimes I sound like I did when I was 12/13 for a split second.

It doesn't happen as much after I've warmed up, but it still slips every now and then. I'm not quite sure my vocal range, I can sing the notes and I don't give it much thought from that. I can't go much lower than F on the low-E string (sometimes I can get the E or a low D) or much higher than the C note on the 10th fret of the D string, sometimes I get the D... if that helps.

Will it go away with time? It has gotten better, maybe it's jus ta practice thing?

Thanks
#2
So your range is F2-D4 if I'm not mistaken. What you're talking about, the sound of a 12yo as you call it, is called falsetto. That's absolutely normal. It won't go away with time unless you practice with the correct exercises. But yes it can be fixed.
#3
it's normal that your voice cracks while flipping from full voice to falsetto as the vocal folds have a change of configuration.

To smooth out the the transition, you can find out about "mixed voice".
A tricky exercice to build up control is also the "messa di voce" exercice : you sing a pitch softly in falsetto, then you go louder until turning into full voice, then you go back into falsetto