This is, from what I can tell, four questions in one.
1) How much of strength training about optimally breaking down muscle, even for beginners?
Strength training is always about optimal muscle breakdown. However, there are varying levels of what one wants to achieve strength wise. Are you trying to train for the next strong-man contest? Mr./Mrs. Universe? Recovering from chemotherapy? Sport specific? Each one requires a different regimen, but all are geared towards optimal muscle breakdown.
Endurance training for your muscles is different as well. This style is more about getting to a certain strength point and being able to repeat the movements a lot. An elderly person, for example, would want to endurance train their muscles to help them with activities of daily living (getting out of a chair, lifting groceries, taking stairs more easily, etc.).
2) How many sets and repetitions would one need to do to achieve an optimal breakdown?
There are so many ways to answer this question it is ridiculous. It really depends on what you are trying to achieve.
3) What are appropriate rest times between sets, and then between workouts?
See question two.
4) When do routines need to be changed to keep having an optimal effect?
This depends on what you are trying to achieve... Bulking-up? Change more than you stay the same (this is still debatable, I was thinking for starters though). Just want to be able to get groceries out of the car? Don't need to change once you get to a weight that you feel meets your grocery lifting needs.
This question is VERY broad and I hope a couple of other posters can help expound on my answers.