Yes, nowadays macs come with 1 Gigabit Ethernet port. check out the tech specs at apple.com
Doesn't matter if your connected to a LAN or not. The MAC address is hard coded into the NIC and does not change unless software on the computer requires that it changes.
It depends what you want to connect to the Mac. It could be the FireWire socket, a USB socket, or the DVI port .
MAC address
The MAC address is the LAN/Ethernet card address there is no specfic Mac address for active directoy. Each server/PC in the world has its own unique mac address.
Yes.
It's being reset too.
MIDI equipment connects to a Mac via an adapter which connects the MIDI socket to a USB socket. These are widely available from electrical/musical stores and suppliers such as Amazon.
A NIC or Network Interface Card/Connection. Your computer should have a LAN interface. You can identify it with RJ45 socket (has 8 pin connector slightly bigger than a telephone socket). If it is there already ensure than the LAN port is enabled in operating system. This port need to be connected to a working LAN network socket which comes through a switch/hub/router.
It identifies the computer on the LAN.
You'd need to be more specific about the make and model of the motherboard when it comes to what will and won't work with your Mac - knowing the processor socket isn't enough information to say one way or the other.
There is no such thing as a LAN card. LAN stands for Local Area Network. The card which communicates with a LAN is called an "Ethernet" card. This Ethernet card/controller may be a separate card but in modern computers is more likely to be a single chip built onto the motherboard. The presence of the chip/card will be indicated by an RJ45 connector/socket on the back of the computer.
To allow you to connect to wireless internet