Genetic code is

The genetic code of the checkerboard (codon table) is not applicable to which of the following?

In sickle cell anaemia,glutamic acid is replaced by valine. Which of the following codes for glutamic acid?

Khorana and his colleagues synthesized an $RNA$ molecule with a repeating sequence of $U$ and $G$ nucleotides. The $RNA$ sequence "$UGU\ GUG\ UGU\ GUG$" produced a tetrapeptide with alternating chains of cysteine and valine. The codons for cysteine and valine are, respectively:

Select the incorrect statement$(s)$.
$i.$ Six codons do not code for any amino acid.
$ii.$ Codon is read in $mRNA$ in a contiguous fashion.
$iii.$ Three codons function as stop codons.
$iv.$ The initiation codon $AUG$ codes for methionine.

There is only one possible sequence of amino acids when deduced from a given nucleotide sequence. However,multiple nucleotide sequences can be deduced from a single amino acid sequence. Explain this phenomenon.