Can you have 2 active bands or are they connected to the same park ticket? Since they are sending out new ones right now with each trip.
Does the magic band have to go through the entrance to the park turnstiles to be activated for the rides that day? Or are they activated already and going through the turnstile has nothing to do with it?
Yes, you can have multiple MagicBands associated with your MyMagic profile, and you can use whichever one of them you like, as long as your tickets are associated with your profile and each band. And you can associate the ticket with multiple Magic Bands via that profile.
If you go stay onsite 3 times this year, you are going to end up with 3 magic bands, each of which are attached to your personal profile, and each of which has your ticket(s) and/or APs associated with it.
The magic bands are always active, so to speak. The RFID chip in the band is always readable, anytime anywhere, with the correct equipment (until the battery in the band dies, which presumably will take years). The band being "alive" is not what gets you into the park. As to whether your band works on the park entrance scanner, it only works if you have an active AP or ticket associated with your MyMagic profile. And of course you provide a matching fingerprint.
When you approach an entry scanner, and put your band next to it, the system reads the RFID in the band. Then it hops out to the central computer system(s) to check if you have a valid admission media attached to your profile, and a fingerprint to match against. If you don't have an active ticket or AP associated with your band, when trying to enter the park the Mickey head will stay blue, and the CMs will pull you aside to figure out why you don't have admission media set up correctly (which could be as simple as resetting your fingerprint, or as complicated as sending you back to the ticket booth to buy a ticket, or to add an association for a valid ticket you bought elsewhere and carried in yourself).
Right now, because we had 2 onsite resort trips with MagicBands, our Annual Passes are associated with 2 sets of MagicBands and we can use either band to enter a park, on a per person basis. So I have my two bands, my spouse has his two bands, etc. We picked different colors for the first and second trips. ;p
I hope that helps...