What is the number of $\sigma$ bonds in $1$-butene?

In polyenes that contain differently substituted $(C=C)$ double bonds,it is possible to hydrogenate chemoselectively one $(C=C)$ double bond. The product of the reaction of limonene with one mole of $H_2$ in the presence of $PtO_2$ is:

Identify the major product formed in the following debromination reaction:
$CH_3-CH(Br)-CH(Br)-CH_3 \xrightarrow{-Br_2} \text{Major product}$

Product $B$ may be :

When neopentyl alcohol is heated with an acid,it slowly converts into an $85:15$ mixture of alkenes $A$ and $B$,respectively. What are these alkenes $?$ (Note: $A$ is the major product and $B$ is the minor product.)

Which reagent converts propene into $1$-propanol?