Which of the following catalysts is used to convert an alkyne $(-C \equiv C-)$ to form a $cis$-alkene?

The major product $(P)$ in the reaction
$Ph-CH=CH-CH_2Br \xrightarrow{HBr} ?(P)$
$[$where $Ph$ is $-C_6H_5]$ is ....

Write the main product of the given reactions:
$(1)$ $CH_3CH = CHCH_3 + HBr \to$
$(2)$ $CH_3-C(CH_3)=CH_2 + HBr \to$

Which of the following alkenes is most easily formed by dehydrohalogenation of alkyl halides?

Ozonolysis of which one of the following compounds produces acetone and $2-$pentanone?

In hydroboration-oxidation reaction $:-$
$I$. Syn addition takes place
$II$. Reaction proceeds through the formation of a cyclic transition state
$III$. Vicinal diol is obtained as a product
$IV$. Anti-addition takes place and Anti-Markovnikov rule is followed
Which of the following statement$(s)$ is/are correct $:-$