RE: anthem mic/pickup

I can't find info online for the following:

1. difference between the "Anthem" and "Anthem SL"
2. the manual implies that there is a pickup mounted under the bridge saddle, is this correct?
3. where is the battery located and how hard is it to replace?

If buying a new guitar, does installation of anthem void the guitar manufacturer's warranty?

thanks for your considered reply in advance,
ohillary