Is "throwing" casual games against the ToS?

I have a friend who is also kind of an unofficial student, and recently I challenged him repeatedly to a casual game just so I could help him drill a certain opening. I would end each game by resigning then repeat the game with him. Seemed easier than creating a study. This is fine, right? Unrated games so there's no manipulation.

Yes it’s totally and absolutely legal, now close this forum

It's fine I'm pretty sure but you can also keep sending takebacks until you are back to the original board.

If its a casual game then i think its fine, in rated thats another story