Do basic solutions also have $H^+_{(aq)}$ ions? If yes,then why are these basic?

While diluting an acid,why is it recommended that the acid should be added to water and not water to the acid?

Metal compound $A$ reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Why does an aqueous solution of an acid conduct electricity?

$A$ solution reacts with crushed egg-shells to give a gas that turns lime water milky. The solution contains:

$10 \,mL$ of a solution of $NaOH$ is found to be completely neutralized by $8 \,mL$ of a given solution of $HCl$. If we take $20 \,mL$ of the same solution of $NaOH$,the amount of $HCl$ solution (the same solution as before) required to neutralize it will be ...... $mL$.