all of your questions......you answer them and lead the way! 10 pounds over my head.....probably.....
I would but I am very long winded, but yes, I can do a lean and press of 10 lb bag of russets. Straight over my head!
I don't think 10lbs would require my maximum strength, so I will disagree. Definitely 20lbs would be hard for me but I'm sure there are people that would find that weight easy too.
i'm not sure what conditions or limitation the op had in mind, but picking up a ten pound bag of anything and holding it over my head briefly is not a big thing. if i were going to carry it around i'd set it down on my head or on my shoulder. i've lifted 50 and even 100 pound sacks of rice to my shoulder and carried them a distance of close to 100 feet, unloading them off of a truck continuously for several hours. exercise for the sake of exercise has never interested me, but i don't mind doing something like that, even getting paid minimum wage for doing so.
I used to work out with a bag of potatoes 3 times a week when I was in high school. I think I was up to benching a 30 lb bag before I strained my shoulder. It might have been 20 lbs, I can't remember now.