$2-$pentyne on reaction with sodium in liquid ammonia produces compound $A$. What is $A$?

Which of the following is Lindlar catalyst?

Which of the following does not belong to the same homologous series?

One mole of $1, 2-$dibromopropane is reacted with $x$ moles of $NaNH_2$ followed by treatment with ethyl bromide to yield a pentyne. What is the value of $x$?

The major product of the following reaction is:

The number of acidic hydrogen atoms in $but-1-yne$ is......