#2
i'm not quite sure i understand what you are wanting to do.... are you saying that you wanna mic your acoustic and plug it into an electric amp and plug a mic for vocals into an electric amp and then record from like an output line out of the amp?
#3
yes- potentially

but also being able to mic either singing or guitar or both so that i can hear myself singing even when im letting rip on the guitar.

i am wondering if it works to use say a condenser mic to pick-up my vocals and guitar and then putting it through just a normal amplifier. And then potentially be able to record that using the line-out port
#4
you can definitely do that... but it isn't going to give you the best sound quality.