Which of the following has the most acidic proton?

$CH_3-CCl_3$ $\xrightarrow[(2) H^{+}]{(1) KOH_{(aq)}}$ $P$ $\xrightarrow[(2) \Delta]{(1) Ca(OH)_2}$ $Q$; $Q$ is:

Oxalic acid reacts with concentrated $H_2SO_4$ to give a mixture of two gases. When this mixture is passed through caustic potash,one of the gases is absorbed. What is the product formed by the absorbed gas with caustic potash?

The reaction $R-CH_2-CH_2-COOH \xrightarrow[Br_2]{Red \ P} R-CH_2-CH(Br)-COOH$ is called as:

The decreasing order of acid strengths for the following compounds is: $Ph-OH$ $(A)$,$Ph-CH_2-OH$ $(B)$,$Ph-CO_2H$ $(C)$,$Ph-CH_2-NH_3^+$ $(D)$

Identify $A$ and $B$ in the following reaction: