Point 1 is explained here:
http://www.cockos.com/ninjam/
In brief, because even at light speed, finite distance cannot be crossed without delay, there will always be some elapse time in communicating between any two points on Planet Earth. The internet does not run anywhere close to light speed and, indeed, doesn't even run reliably at any one speed most of the time, so you also need buffering. NINJAM takes care of this by ensuring participants all know where "1" is. Each participant's "1" is always in line with the others'. However, it's not the same "1" -- you'll hear your "1" "now" but other participants will have to wait until it's been buffered to line up with their "1".
Point 2 is explained here:
http://www.cockos.com/ninjam/
In brief, no, there is other software available (see above link). However, Reaper will probably give the most pleasant experience.