Answer:
Answer No 3: Recent studies and researches have shown that the muscle cells do not actually wear and tear during heavy exercises. What happens is that micro tears are formed in the muscle fibers as a result of heavy exercise. These micro tears cause the muscle cells to rebuild themselves.
Answer No 4: One of the biggest reasons that the insertions done by CRISPR-Cas9 insertion would not pass to future generations is because the specialized cells are being modified in this system. As the specialized cells do not have the tendency to for all cells of the body hence, the insertion made by CRISPR-Cas9 will most likely not be transferred to the future generation.