Second off, while listening to the pronunciation closely I'm hearing "zupel-wenie" (as one would read it in english), but I'm doubting my ears and I'm guessing it to actually be "zupe-wenie", without the L sound.
Well, it's certainly not a bad idea, but I don't think it's absolutely necessary, as 99% of the TTS recordings here are actually quite good. And I think that this one is fine, too.
Confused by why 'zupelnie' is not at the beginning of the sentence when, in previous sentences, this was the case and, as I understood it, thus emphasises the completeness?
No. The word "zielony" can be used in that meaning as addition to nouns that by no means could possibly be actually green - generally abstract nouns. "Zielona energia" and "zielone technologie" are the only two that I can bring to my mind at this moment.
I asked a British native speaker from our team and she's not convinced, saying that if we were to use "absolutely" here, it would rather be something like "That cheese is absolutely green with mo(u)ld".