boiling the divacup

i really want to clean it so i was thinking of boiling it but im afraid that i might explode it or something. how long should i leave it boiling? should i stir it? sorry if this question seems pretty stupid, i've never done this before and i don't want to ruin my cup. also, is it bad to sterilize it with alcohol? like rinse it in alcohol? and while im on the topic of cleaning: i've seen a lot of cups that have gone a golden color after a few years/months of use. how do i prevent that from happening? thanks in advance :)