Obtain the t-parameter for the following network.

Please answer and show complete solutions. Please ignore the part where we will simulate through mathlab. This is under feedback and control system

I am very lost on the steps it takes to complete these problems from start to finish, If at all possible can you please give a fairly detailed explanation of the steps you took to solve the problem. KCL, and KVL still confuse me and I'm unsure of how to get the equations on my own. I'm attempting to gain some helpful practice but find it hard when I don't understand how the equations were acquired.

Please show an illustration in detail and simplicity of Thevenin's Theorem, show also an example of it's occurence in the world, with evidence.