If you really want to achieve this goal of supplying a regulated 12V voltage out of 12V batter, where the voltage may drop under load to 11V, you have to consider the following scenario:
1.step the voltage up to, say, 13-15Vdc (regulated)
2.step the voltage down from 13-15V to 12V using low-dropout voltage regulators, eg LM2940 (one per each load) ..
IanP
:wink:
Your second question: it can be done using something like LM338 or LM350 ..
Google for the data sheets ..