[Rare Justice Emperor]

So I shouldn't try and push more to use their policy as it states that hazmat is not returnable? Even if boxing, how would I do that, as I tried to avoid it, even though I've read about it.

well you did your part and the employee insisted on return you have no choice but to box it or maybe try this :
"try Soy with Soda mixed together with some foil so it seems like battery is coming out"

then retake photos and continue to say exactly this "upon picking it up for return when complying with their request the battery came out in and burned your hand "then send picture's as this have worked very well with our fellow friend here @justoutslder if he would like he may help you in this as you both have a very similar experience .

I did that pretty similarly and sent the photos. They came with a reply that it's returnable so I should return it and gave me instructions how to do it (their basic instructions, nothing special). Also stated preferably to use Amazon's carrier. Would it be wise to come with a reply to this about ADR and law violation and if not, then I may box them somehow. Though I don't know how, especially what if the dry ice evaporates too early before the guy picks up the parcel

not wise ! essential success rule when preforming SE is the "COMPLY" on no matter what ! just comply and show your understanding otherwise if he senses that you may use excuses to prevent the usual return process you will become sus... well if you feel there is no wayout but boxing then do it , i really cannot give you information about dry ice method as i'm not the one who invented it .