(A) : ${{\left[{\mathrm{SiF}}_6\right]}^2}^{‑}$ is formed but ${{\left[SiC{l}_6\right]}^2}^{‑}$ is not

(R) : Electronegativity ($EN$) of $F$ is higher than $EN$ of  $Cl$

Six large chloride ions cannot be accommodated around ${\mathrm{Si}}^{+4 }$due to limitation of its size. 

A is correct.

F is more electronegative than chlorine, in fact it is most electronegative element of the periodic table but its electron affinity, the tendency to accommodate electrons, is less than the Cl due to non availability of d-electrons.

R is incorrect.