Identify the correct statements about lanthanoids

I. $\mathrm{Ce}^{4+}$ and $\mathrm{Tb}^{4+}$ act as oxidising agents.

II. $\mathrm{Eu}^{2+}$ and $\mathrm{Yb}^{2+}$ act as oxidising agents.

III. Misch metal is an alloy of $95 \%$ iron and $5 \%$ lanthanoid metal.

IV. $\mathrm{La}^{3+}$ and $\mathrm{Ce}^{4+}$ are diamagnetic in nature.

When 100 mL of 0.2 M solution of $\mathrm{CoCl}_3 \cdot x \mathrm{NH}_3$ is treated with excess of $\mathrm{AgNO}_3$ solution, $3.6 \times 10^{22}$ ions are precipitated. The value of $x$ is $\left(N=6 \times 10^{23} \mathrm{~mol}^{-1}\right)$

Ethylene on reaction with cold, dilute alkaline $\mathrm{KMnO}_4$ at 273 K gives a compound ' $P$ '. This on polymerisation with which of the following gives dacron?

A carbohydrate $(A)$, when treated with dilute HCl in alcoholic solution gives two isomers $(B)$ and $(C)$. $B$ on reaction with bromine water gives a monocarboxylic acid ' $Z$ ' and ' $C$ ' is a ketohexose. What is $A$ ?