DANISH ENDURANCEMen's Briefs Multipack, Classic Soft Cotton Briefs, 6-Pack

What temp can i wash these at? Too many products say max 30°c max, which isnt sanitary.

Do these stretch over time and with regular use? I find them a great everywhere apart from the front where they are painfully tight!

Is it made in china? (i don't care about the usual "designed in __" bs)

What size should i get for a 36inch waist? l or xl?