I'll just leave this here: http://justjuice.org/the-un-juiceables-a-to-z-list-of-fruits-and-vegetables-that-just-wont-juice/
"total gerne" is an expression a German speaker would never use. Sehr gerne, wirklich gerne would fit the bill.
Is there any reason that Bananensaft, Ornagensaft, Tomatensaft are in the plural form, while Apfelsaft is in the singular form? Is it random or the apple juice is the only exceptional?
I think it has the same meaning (you associate drinking banana juice with positive feelings^^), but it varies in intensity and has a different grammatical structure... which seems to matter a lot to duo. I would translate it as "Ich liebe es Bananensaft zu trinken."
Considering how we American use "love", to translate" I really love to drink banana juice" should be accepted!
No. According to responses/comments I read from other users on this forum and also from the link I gave below there is no difference. Gerne is the regular form and gern is just a colloquial variation.