Carbon-carbon bond length is minimum in

Predict the product of the following reaction sequence:
$HC \equiv CH$ $\xrightarrow[\begin{smallmatrix} (2) \text{ excess } I-CH_2-(CH_2)_2-CH_3 \\ (3) \text{ } H^{\oplus} \end{smallmatrix}]{(1) \text{ excess } NaNH_2}$

Which of the following metal carbides gives propyne on hydrolysis?

$CH_3-CH_2-C \equiv CH \xrightarrow{R, H_2O} \text{Butanone}$. $R$ is:

Which of the following compounds on hydration (addition of $H_2O$) with $H_2SO_4/HgSO_4/H_2O$ gives an aldehyde as the major product?

The reaction of calcium carbide with water produces.......