Which of the following compounds has the most acidic hydrogen?

In the reaction
$Phenol$ $\xrightarrow[\text{Reimer-Tiemann}]{} X$ $\xrightarrow[(ii) H^+]{(i) NaOH \text{ (conc.)}} Z$
Product $Z$ is

$2Ph-CHO \xrightarrow{OH^-} Ph-CH_2OH + PhCOO^-$
Which is the slowest step in the above Cannizzaro reaction?

Ketone reacts with $NH_2OH$ to give oxime. The reaction is as follows:
$R_2C=O + H_2N-OH \rightarrow R_2C=N-OH + H_2O$
The total number of organic products (ketoxime) formed when the simplest ketone and its next higher homologue react with $NH_2OH$,is:

The structure shown in the figure is best classified as a(an):

In Tollen's test for aldehyde,the overall number of electron$(s)$ transferred to the Tollen's reagent formula $[Ag(NH_{3})_{2}]^{+}$ per aldehyde group to form silver mirror is $......$. (Round off to the Nearest integer)