Fehling solution reacts with $HCHO$ to form a precipitate of which color?

Which of the following on reaction with Grignard reagent followed by hydrolysis forms a tertiary alcohol?

What will be the main product in the following reaction?
$C_6H_5CHO + CH_3CHO \xrightarrow{OH^-, \Delta} ?$

In the given reaction,$X$ can be:

For the conversion of cyclohexanone to $1-$hydroxy$-1-$methylcyclohexan$-2-$one,the correct order of reagents used is:
$(1)$ $CH_3MgBr / H^+$
$(2)$ $H^+ / \Delta$
$(3)$ $KMnO_4$ (cold dil.)
$(4)$ $CrO_3$

What will be the product $B$ in the following sequence of reactions?
$HC \equiv CH$ $\xrightarrow{30\% \, H_2SO_4, \, HgSO_4} A$ $\xrightarrow{NaOH} B$