What is the correct order of $K_a$ values for the given compounds?

The cyclic cations having the same number of hyperconjugation are: Choose the correct answer from the options given below:

Identify the species from the following that exhibits no-bond resonance (hyperconjugation).

What is the type of delocalization involving $\sigma$ bond orbitals called?

With respect to the compounds $I-V$,choose the correct statement$(s)$.
$(A)$ The acidity of compound $I$ is due to delocalization in the conjugate base.
$(B)$ The conjugate base of compound $IV$ is aromatic.
$(C)$ Compound $II$ becomes more acidic,when it has a $-NO_2$ substituent.
$(D)$ The acidity of compounds follows the order $IV > V > I > II > III$.

What is the correct order of decreasing acidity for the following compounds?