Which of the following has zero inductive effect?

Fill in the blanks:
$(1)$ In $+E$ effect,$\pi$ electrons from a multiple bond migrate to the ........... .
$(2)$ In $-E$ effect,$\pi$ electrons from a multiple bond migrate to the ........... .
$(3)$ ........... and ........... increase stability.
$(4)$ ........... inductive effect increases the acidic strength and ........... inductive effect decreases the strength of $-COOH$.

What is the order of $-I$ effect in orbitals?

Among the following,the most acidic compound is

In compound $(X)$,hyperconjugation is present and in $(Y)$,resonance effect is present. What are $X$ and $Y$,respectively?

Which of the following groups does not show $(+R)$ effect?