Master genes, which are the genes in the DNA that control major development processes such as the development of the skeleton, the organs etc and the production of the necessary proteins.
Since they take on such an important role, they don't really change much. Master genes that affect development tend to be highly conserved so embryonic development can show similar patterns.
The second one's answer is : Mature nerve cells, cardiac muscle cells, skeletal muscle fibers, fat cells, red blood cells, bone cells (osteocytes), and white blood cells (except lymphocytes) do not undergo division
