Few questions relating to my new Rainbow Lorikeet

by Hailey

A few days ago we purchased a 10 week old Rainbow Lorikeet. He is extremely affectionate and gentle except when we lay him on his back. When we bought him we were told to get him use to laying on his back while he is young because it will be easier to train him to do this now rather than later. The day after we bought him home I was laying on my bed with him and he rolled over on his own and let me scratch his belly, he has done this every day since so I assume the people who had him before us were doing this with him, it is really cute and I'd like to continue doing this with him but he bites extremely hard when he is on his back and I don't want to promote this particular behavior for obvious reasons.

I have taken to giving him a stick off a tree to chew on when he wants to roll over to save my fingers but I'd like to understand why he does it and if there is a way to teach him to use his "soft" mouth when playing like this.

I don't think he's doing it because he doesn't like being on his back because most of the time he instigates this. I thought maybe he just doesn't want to be touched on his belly but if I stop he rolls back over and nibbles (gently) on my fingers. any advice or insight would be much appreciated on this matter.

Finally I wonder how often I should offer him a "bath"? I was told he loves water and to offer him a shallow tray of clean water to play in. I did this yesterday and at first he wasn't interested at all but after a few minutes he got in and went crazy! He was rolling around, screeching and flapping his wings. He even managed to give me a bath in the process! should I offer this to him daily, a few times a week? less often?