Complete the following reactions:
$(i)$ $C_2H_4 + O_2 \rightarrow$
$(ii)$ $4Al + 3O_2 \rightarrow$

Which of the following alkenes gives both $cis$ and $trans$ isomers upon catalytic hydrogenation?

$CH_3-CH=CH_2 \xrightarrow{HBr} \text{Major product } (A). \text{ } A \text{ is:}$

How can ethene be produced from ethanol?

Identify the relationship between $A$ and $B$ in the following reactions:
$CH_3-CH=CH_2 \xrightarrow[(2)H_2O_2, OH^-]{(1)BH_3-THF} A$
$CH_3-CH=CH_2 \xrightarrow[(2)NaBH_4]{(1)(AcO)_2Hg, H_2O} B$

$1-$Propanol can be prepared from propene by