You've asked four questions and two have been downvoted by me. I don't believe there have been other downvotes.
- Your first question hasn't been downvoted but, has been answered yet, you have not recognized any usefulness in that answer because you don't appear to have upvoted it. Do you have a reason for this?
- Your 2nd question contains this profoundly wrong assertion: -
Most signals in the world are analog and in order to study them, filter them, or amplify them, we need to represent them digitally.
I mean, consider the Andromeda galaxy; it's distance was first calculated in the 1920s by Hubble (the person); do you think he used digital methods?
So, I downvoted it because of that and, stopped reading any more. The message is clear; your question indicates no sign of proper research (a perfectly valid reason for downvoting).
from what i understand when we are looking at a linear circuit with independent sources while being interested in describing the electrical properties of the system at the terminals
It's an incomplete sentence.
Your 2nd sentence (really a 6 line paragraph) is some kind of preamble to what you are going to ask but, it's couched in such a way as to be fairly undecipherable. Your 3rd paragraph/sentence is also coming over as undecipherable: -
now what i am interested in asking (assuming i grasped the basic intution) is first regarding the cases when internal dependent sources exists ,while proving i did not take them into account , when they exist do i basically turn them to shortcuts and open circuits to find...\$R_t\$ and keep them when doing the internal part ?
Your next paragraph/sentence is a shopping question (See What topics can I ask about here?)
secondly in case of non linear circuit i can't use Thevenin since proving it required linearity are there similar tools for non linear circuits that i can read about for future reference ?
So, at that point I downvoted and moved on.
My advice is plan your question and stick to that question. No need to try and support your question with badly presented theory or erroneous assertions. I find that it's harder to write a good question than to write a good answer and, the reason is because there is a clear focal point when making an answer. Try and make a clear focal point when asking a question.