Which is the major product of the following reaction?

Find the major product of the following reaction: $C_6H_5CHO + CH_3CHO \xrightarrow{Ca(OH)_2, \Delta} ?$

Calcium butanoate on heating followed by treatment with $1,2-$ethanediol in the presence of a catalytic amount of an acid,produces a major product which is

Which of the following reagents can form a hydrazone with alkanone?

In which of the following reactions is the product $NOT$ correct?

An organic compound $(X)$ with molecular formula $C_3H_6O$ is not readily oxidised. On reduction it gives $(C_3H_8O)$ $(Y)$ which reacts with $HBr$ to give a bromide $(Z)$ which is converted to a Grignard reagent. This Grignard reagent on reaction with $(X)$ followed by hydrolysis gives $2,3-$dimethylbutan$-2-$ol. Compounds $(X)$,$(Y)$ and $(Z)$ respectively are $:$