How does choice of Physical media affect the Link Layer?

What is the primary purpose of the Link Layer?

In a network architecture for a large$-$scale installation, what is the purpose of the:

a$.$ Access Layer

b$.$ Distribution Layer

c$.$ Core Layer

How does this design help with

a$.$ Scalability

b$.$ Reliability

Link Layer frames use the MAC address of the sending node and the receiving node, how are these different from the IP address?

Describe what happens, related to the Link Layer frames, to an IP packet as it makes its way from machine A $$ switch $S1$ router R$1$ switch $S2$ machine B$.$

PLEASE ANSWER AS MANY AS YOU CAN