generally, teams use defensive formations to mirror what the offense is using. if a team is using two wide receivers, you'll see a 4-3 formation - meaning that there's four linemen on the line, three linebackers in the middle, and four DBs in the secondary. nickel refers to the fact that there's 5 DBs on the field - teams bring on one extra DB to cover the third WR, and leave one LB on the sideline (depending on the team, either the LOLB or the ROLB). in turn, dime has six DBs and one LB, and quarter has seven DBs (for 3rd and 20, or to defend a hail mary), one LB, and only 3 linemen (they drop the second DT).
4 deep would be to defend against the big pass - preventing a bomb but allowing them to get yards underneath. if it's 3rd and short, use a formation that stacks the line or blitzes the LBs.
roster updates depend - i don't know if they're supported now that the new season is upon us.
punting is easy. you hike the ball, pull the right stick back to charge it, and throw it forward to actually punt it. use the practice mode - it helps a LOT. if there's another type of mode that you need help with, ask me - i've played every madden since 2000. i love football games, and i have no problem paying the money for what equates to a roster update simply because i WANT those players on my team.