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

What are the products formed when an aldehyde $(R-CHO)$ is reacted with Tollen's reagent?

The reagent$(s)$ which can be used to bring about the following transformation is(are):
$(A)$ $LiAlH_4$ in $(C_2H_5)_2O$
$(B)$ $BH_3$ in $THF$
$(C)$ $NaBH_4$ in $C_2H_5OH$
$(D)$ Raney $Ni / H_2$ in $THF$

$A$ carbonyl compound $P$,which gives a positive iodoform test,undergoes reaction with $MeMgBr$ followed by dehydration to give an olefin $Q$. Ozonolysis of $Q$ leads to a dicarbonyl compound $R$,which undergoes intramolecular aldol reaction to give predominantly $S$.
$P$ $\xrightarrow[\substack{2. H^{+}, H_2 O \\ 3. H_2 SO_4, \Delta}]{1. MeMgBr} Q$ $\xrightarrow[2. Zn, H_2 O]{1. O_3} R$ $\xrightarrow[2. \Delta]{1. OH^{-}} S$
$1.$ The structure of the carbonyl compound $P$ is
$2.$ The structures of the products $Q$ and $R$,respectively,are
$3.$ The structure of the product $S$ is
Give the answer for questions $1, 2$ and $3.$

The major product formed in the following reaction is:

The reactant is $3$-methylpentanal. The reaction with $NaCN$ followed by $H_2SO_4$ (cyanohydrin formation) is shown below:
$CH_3CH_2CH(CH_3)CH_2CHO \xrightarrow{NaCN/H^+} CH_3CH_2CH(CH_3)CH_2CH(OH)CN$
Products of the reaction are: