Question 1: No, but each time Southwest extends its booking period, it also displays (well, within a couple of days) approximately when the next round of fares will be released.
Question 2.
Southwest does not preassign seats
Buy your ticket/s
Check in online no more than 24 hours before your flight
Your boarding pass will indicate if you are in boarding group "A", "B", or "C".
In addition, it will have a number on it - usually A21-A60, B1-B60, C1-C60*
At boarding time, the Gate Agents will first allow passengers with medical needs to board, then boarding passes through A20.
Then, having had the A group line up by poles with their number ranges (21-25, 26-30, 31-35, etc), they will allow those passengers to board.
Then passengers (immediate, not extended, families) flying with children four and under will board; then the B group will have lined up like the A group did, and board in order; and finally the C group.
You can sit anywhere not already occupied by another passenger; but you should not expect any passenger already on board to move to another seat so you can "all" sit together.
*A1-A15 are reserved for high-fare business passengers; A16-A20 are for SWA's elite fliers; if your flight originates elsewhere and connects in your city, the pool of number will be smaller but the boarding passes will still be split among A/B/C.