Show us the evidence that in Earth’s primordial oceans, after millions of years, there were no more than 20 different amino acids.
Tele - you are missing the point. It doesn't matter have how many amino acids were potentially available, what mattered was which ones were able to create stable peptides and proteins in the conditions that existed at the time. Remember the conditions at that period were completely different to conditions today. Particularly relevant to peptide chemistry are the levels of radiation and pH both of which are able affect the tertiary structure of longer amino acid chain peptides and proteins.
Anyway what about responding to the video I posted?