RIPT Boy's Essentials Swim Shorts Quick Dry UV 50 Sun Protection Swim Shorts

Do the shorts have a lining?

Does anyone know the waist measurement for size 3-4? I bought 5-6 for my slim 7 year old and it was way too big.

My son is super slim to do growth issues. He needs 5-6 length but trunks always fall down. Are these good for slim kids?

Do they have side slits ?