I think that the front sockets are just for convenience as this unit is designed for rack mounting and most of the sockets would be difficult to get at (behind the rack). Does the manual say anything about them? I know someone that has one of these and they are great value for money and a well thought out design. I don’t know if it works with Audacity as he uses other software. The mic pre-amps are not the quietest in the world, but in this price range Tascam have crammed in a lot of bang for your buck.
Microphones should always be plugged in with XLR connectors. If a microphone has a jack plug on the end it is probably a cheap and shty mic. Hybrid sockets are frequently used to allow instruments to be plugged in directly.
See also:
and
When you eventually get a multi-channel device it would be great if you could post a review.