The geometry of the reaction intermediate in an $S_N1$ reaction is:

Which of the following carbocations is most stable?

Stability order of the following carbocations is:
$(i)$ $CH_3-C^{+}(CH_3)-CH_2-CH_3$
$(ii)$ $CH_3-CH^{+}-CH_3$
$(iii)$ $CH_3-C^{+}(CH_3)-CH_3$
$(iv)$ $Ph-CH^{+}-CH_3$

What is the correct order of stability for free radicals?

Most stable carbocation among the following is:

Based upon an understanding of product stability,predict the product formed when the following dianion reacts with one equivalent of acid $(H^+)$.