Clear questions, tried to be as clear as possible in answering !
1) In theory, helping new players understand the game more quickly and recieving (minor) experience bonusses, in reality, powerleveling lower levels to gain honor points for honor weapons and honor buffs.
2) At level 60, at the cost of 100.000.
3) Not a darn thing at all, beside the ability to recruit pupils and via them gain a minor experience bonus and possibly honor points.
4) Guidance, a minor experience bonus and possibly a new friend.
5) It's that minor experience buff, as a lower levels grinds he/she gets points, those points can be sent towards to the academy leader to give both a minor experience bonus.
6) The lower one joins, the lowers its beginning rank (and the more honor points when he/she graduates), they eventually can get up to gaurdians.
7) No, would be funny though, outleveling your "master".
"8)" Yes, if you plan to powerlevel lower level friends to gain honor points for either a honor weapon or honor buffs, prepare for a long-term powerleveling situation, I was bored after 1, so good luck