Which reagent is suitable for the following transformation?

Arrange the following reagents in the correct order in which the above transformation is carried out:

Given below are two statements:
Statement $I$ : Acidity of $\alpha$-hydrogens of aldehydes and ketones is responsible for Aldol reaction.
Statement $II$ : Reaction between benzaldehyde and ethanal will $NOT$ give Cross-$Aldol$ product.
In the light of above statements,choose the most appropriate answer from the options given below.

Predict the product $X$ for the following reaction:
$2\text{-oxocyclohex-3-en-1-yl} \text{ acetate derivative} \rightarrow{NaBH_4, MeOH} X$

The mass of $NH_3$ produced when $131.8 \ kg$ of cyclohexanecarbaldehyde undergoes Tollen's test is $..... \ kg$. (Nearest Integer) Molar Mass of $C = 12 \ g/mol$,$N = 14 \ g/mol$,$O = 16 \ g/mol$.

In the following reaction:
$\text{Aldehyde} + \text{Alcohol} \xrightarrow{HCl} \text{Acetal}$
$HCHO \qquad ^tBuOH$
$CH_3CHO \qquad MeOH$
The best combination for the formation of acetal is: