1. How do you sync?
There are buttons on each speaker that allow you to set a master speaker and then set the other one up as the slave. The instructions show you how to do it. Very simple.
2. Are these batteries powered or electric?
Ther are battery-powered. Built-in 6,600mAh rechargeable battery, fully charged within 3 hours, up to 20 hours playtime at Medium Volume or 10 hours at Max.
3. Do the speakers have an aux port, and can you plug in an older style iPod without Bluetooth?
Yes, the speakers have an aux port.
4. Are these speakers waterproof enough to be left/kept outside?
Being IPX5 waterproof, the speaker is splashproof and rainproof.