Which of the following alkenes is the most stable?

According to Markovnikov's rule,what is the product formed when $1$-butene reacts with water?

Addition of $HCl$ to $3,3$-dimethyl-$1$-butene yields two products,one of which has a rearranged carbon skeleton. Among the following carbocations,select the possible intermediates in that reaction:
$1.$ $(CH_3)_3C-C^+H-CH_3$
$2.$ $(CH_3)_3C-CH_2-C^+H_2$
$3.$ $(CH_3)_2C(Cl)-C^+(CH_3)_2$
$4.$ $(CH_3)_2C^+-CH(CH_3)_2$

$Propanal$ and $pentan-3-one$ are ozonolysis products of:

Find out the major products $A$ and $B$ from the following reactions.

The major products obtained during ozonolysis of $2,3-$dimethyl$-1-$butene and subsequent reduction with $Zn$ and $H_2O$ are