$2,3-$epoxybutane is the anhydride of

$A$ compound with formula $C_4H_{10}O$ on oxidation gives $C_4H_8O$,which forms an oxime and gives a positive iodoform test. The original compound on reaction with concentrated $H_2SO_4$ gives $C_4H_8$. What is the structure of the compound?

The products obtained in the following reaction are:

In the following sequence of reactions,the product $C$ is: $CH_3-CH_2-CH_2-Br$ $\xrightarrow{KOH(alc)} (A)$ $\xrightarrow{HBr} (B)$ $\xrightarrow{KOH(aq.)} (C)$

Lucas test is used for:

The order of ease of dehydration of the following alcohols is:
$I$: $CH_3-CH_2-CH_2-OH$
$II$: $(CH_3)_2CH-OH$
$III$: $(CH_3)_3C-OH$
$IV$: $CH_3-CH_2-OH$