1) Dueling limit is 10 duels
2) I believe the wait is 20 minutes
3) Petrificus Totalus gives the most amount of points and is easy to cast
If anyone has any other answers or questions feel free to inbox them :)
Get your points up for a spell(s) and to stick to that spell(s).
Battle those from other houses, preferably Gryffindor so we don’t widen the gap even more between us and Ravenclaw and Slytherin.
Practice them spells my dears.