I have used an in wall splice with Romex 14/2 that has 3 ports (hot, neutral, ground) but i would now like to use the same method to splice a 12/3 cable. I'm unable to find a splice with 4 ports. Can I just use two regular 3 port splices and divide it 2-2 or 3-1?
You can't, but no need.
If you're referring to the Tyco Electronics Romex splice kits, yes, they make those for 3-wire w/ground as well as 2-wire w/ ground.
If you mean some other splice method, you have to read its instructions for whether it is suitable in-wall. As far as I know the Tyco is the only one that is UL-listed for buried in-wall splicing.
Further, use of in-wall splice blocks is restricted. It can only be done for repair, not extension for instance; and even then, only as a last resort when nothing else is possible. If it is at all feasible for you to re-run the entire cable run, or a run to an accessible point (somewhere you want a receptacle, for instance), you must do that instead.
No, all the conductors need to be part of the same assembly. A 4-hole version is NSi Model # NMS-3, they are about $15 from Home Depot.