The order of reactivity of $C_2H_6$,$C_2H_4$,and $C_2H_2$ is.......

What is the number of $\sigma$ and $\pi$ bonds in $Pent-1-en-4-yne$?

What is the stereochemistry of the product formed in the following reaction?

Compound $A$ $(C_{11}H_{14}O_4)$ is a degradation product of the antibiotic vermiculine. It undergoes the following reactions as shown in the image. Identify the unknown compound $C$ $(C_{11}H_{18}O_2)$.

The double bond equivalent $(DBE)$ of cubane is:

For the following reaction scheme,percentage yields are given along the arrows. $x \ g$ and $y \ g$ are the masses of $R$ and $U$,respectively. (Molar mass of $H$,$C$,and $O$ are $1$,$12$,and $16 \ g \ mol^{-1}$ respectively). $(1)$ The value of $x$ is $(2)$ The value of $y$ is.