If you are asking if you can use rj45 from phone distribution block to wallplate, yes you can.
This is in fact the way most datacomm companies do it as rj45 is cheap and versatle.
To add more phone lines you will have to obvoiusly pay for an additional line from your phone povider.
You can then rewire your distribution block to put some lines ot one phone and some lines to another phone.
You can also get higher end phones that will allow you to wire the blue pair of wires on rj45 with line 1 and the green pair (assuming T568-B wiring) with line 2.