Hi! 1. The first is correct use of hyphens, because it's connecting the years, five-to-ten. The second option leaves a hyphen unconnected to anything, which makes me think there is a break in the sentence where you don't mean for there to be. 2. This one is complicated because it's about slang, where the normal grammatical rules don't really apply. You're right that it's "have fun" correctly, but (especially in songs) people like to twist meanings. "Ain't we got fun" isn't correct at all, but people understand the meaning (basically what you said, "Don't we have fun". It's not common, however. I've never heard anyone say it in conversation. It's more of a playful phrase that isn't meant to be grammatically correct. Hopefully this makes sense!