I’m an annoying millennial I call em acetates cause I figure what they were called in the 40s or thereabouts is good enough for me see. Now I’m off to my ether frolicking and ice cream social daddy o or watever.

Looks like that’s it you got it right. As to what it means here you go. https://www.etymonline.com/search?q=stope

Guess the op yearns for the mines.

I bought 3 packs hopefully it’s like the other recalled or banned stuff and actually good spice.

Yep all 3 are valid, matte is the new variant. https://www.etymonline.com/word/matte#etymonline_v_9722

And I’ve seen all 3 in use in the USA. It’s not matte = Canada. I’ve seen matte more than mat which is historically the spelling. The oed doesn’t list matt as the proper spelling but who knows with the brits.