Which of the following molecules is the most covalent?

Which one is the highest melting halide?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R.$
Assertion $A :$ Lithium halides are somewhat covalent in nature.
Reason $R :$ Lithium possesses high polarization capability.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following chlorides shows the most covalent character?

The number of the following factors which affect the percent covalent character of the ionic bond is $............$.
$(a)$ Polarising power of cation
$(b)$ Extent of distortion of anion
$(c)$ Polarisability of the anion
$(d)$ Polarising power of anion

$AgF, AgCl, NaCl, NaBr, NaI$ are colourless but $AgBr$ and $AgI$ are coloured because