Is evolution a continuous process?

If evolution is a continuous process, why do we see the same 20 proteogenic amino acids in all organisms? Why do we see the same A, T, G and C in DNA of all organisms? Why do we see the same A, T, G and U in RNA of all organisms? Why there is no futher evolution in proteogenic amino acids? why there is no futher evolution in the nucleotide residues which can be the parts of DNA/RNA? Does everything evolve or only certain things evolve? If everything evolves, then there must be evolution in the proteogenic amino acids and the nucleotides which are parts of the genetic mechanism.

Evolution is partially dead.

also evolution happens when two genes merge, if I haven’t misunderstood.

so we won’t get any major changes fast.

Maybe it’s the most optimal combination for sustaining life (on chemical level)…like most mammals having 4 limbs, instead of say 5 or 6.

You have.