Acetals are

Which of the following compounds will form lactic acid from its cyanohydrin?

$CH_3-CHO + CH_3-MgBr$ $\rightarrow \text{Product}$ $\xrightarrow{H_2O} A$. What is $A$?

Predict the products of the following reactions:
$(i)$ Cyclopentanone + $NH_2OH \xrightarrow{H^+} ?$
(ii) Cyclohexanone + $2,4-DNP \xrightarrow{H^+} ?$
(iii) $R-CH=CH-CHO + NH_2CONHNH_2 \xrightarrow{H^+} ?$
(iv) Acetophenone + $CH_3CH_2NH_2 \xrightarrow{H^+} ?$

Which of the following compounds is used to convert acetaldehyde into acetaldehyde cyanohydrin?

Which of the following aldehydes is most reactive $?$