$A \xleftarrow[\Delta]{Cu} CH_3CH_2OH \xrightarrow[\Delta]{Al_2O_3} B$. $A$ and $B$ respectively are

Ozonolysis of $2-$methyl$-2-$butene,in presence of $Zn,$ yields $--$

The Diels-Alder reaction will not take place with which of the following reactants?

Addition of $BH_3$ followed by $H_2O_2$ to $trans-2-butene$ would give a product which is

The major product $(P)$ formed in the reaction below is: $HC \equiv C-CH_2-CH=CH_2 \xrightarrow[CCl_4, 253 \ K]{Br_2(1 \ mol)} P$

$3-$Methylhex$-2-$ene on reaction with $HBr$ in the presence of peroxide forms an addition product $(A)$. The number of possible stereoisomers for '$A$' is $....$.