If you were to receive some turtles as a gift, how would you differentiate "these turtles are from you," from, "these turtles are yours," as both seem to have the translation given above?
Both are the same in Dutch. You would have to choose other words or another construction, for instance 'dit zijn jullie schildpadden' > 'these are your turtles'.
I'm so confused. Why won't "De schildpadden zijn jullie" pass for this? What's the difference so vast it should take away a heart?
That would translate as "The turtles are you" instead of "The turtles are from you" or " The turtles are yours".
Is it correct to use this phrase when talking to a single person and a group of people. Or only for groups (Jullie is the plural version of you, right?)
'Jullie' is indeed plural, so you can only use this phrase when talking to a group. When talking to a single person, the sentence would be "De schildpadden zijn van jou".
Say we brought toy-animals to a party. And then we are confused as to who brought what. In English, we will say something like, "The cows are from me. The birds are from you (all). The lions are from me. The turtles are from you (all)."
In Dutch, then, would you not say the last sentence as "De schildpadden zijn van jullie"?