Yep, I need my Galaxy 23ultra together with the osmo 6. works perfectly.
By the way: there is a compatibility list on the DJI homepage.

Yes, my husband also uses the Osmo Mobile 6 with his Galaxy S23 Ultra.
Everything works perfectly -

Hello Yes I would say my Iphone 15pro max with a protective case from Spigen with a business card compartment at the back. fits.

Yes, you can use all mobile phones. The size can be adjusted.