here are some discussions on foot care
https://forum.tudiabetes.org/topics/foot-care-1
https://forum.tudiabetes.org/topics/feet
https://forum.tudiabetes.org/topics/diabetes-dry-feet-and-sandal
http://www.tudiabetes.org/group/sweetfeet/forum/topics/i-hate-my-toe-nails
and our group for foot issues
http://www.tudiabetes.org/group/sweetfeet
I almost always wear something on my feet, just to be careful. but I do wear sandals and flip flops. cut your nails straight across. do not put lotion between the toes. I would never cut a callous, but sanding them down with a foot pumice, wearing well fitting shoes, and moisturizing will cut down on them. I see no reason why you can't wear nail polish. as for the "feet, not hands" - I don't know. maybe the feet are furthest away from the heart.
make sure your endo checks your feet every visit.