The reaction between cyclobutylmagnesium chloride and cyclobutanol is shown below. Identify the product $P$.

What are $X$ and $Y$ in the following reactions?

The final product $A$,formed in the following reaction sequence is:
$Ph-CH=CH_2$ $\xrightarrow[\text{(iii) } HBr, \text{ (iv) } Mg, \text{ ether, then } HCHO / H_3O^{+}]{\text{(i) } BH_3, \text{ (ii) } H_2O_2, OH^{-}} A$

Identify $P_3$ in the following reaction sequence:

Which among the following compounds reacts fastest with $HBr$?

Which of the following gives a $2^{\circ}$ alcohol as a major product upon reaction with $CH_{3}MgBr$ followed by $H_{2}O$?