How many codons code for amino acids?

The diamond code proposal was made by:

State the salient features of the genetic code.

If the genetic code were a tetraplet (four-letter code),how many possible codons would exist for $20$ types of amino acids?

Which triplet codon acts as a stop signal for the process of translation?

$A$: Triplet genetic code can be confirmed by frame shift mutations.
$R$: Frame shifting involves the change in protein product coded by triplet codons.