For the preparation of alkenes,an aqueous concentrated solution of sodium or potassium salts of carboxylic acids is subjected to ........

Alkenes react with water in the presence of acid to form alcohols. Identify the steps involved in the mechanism of the reaction from the following :
a) Nucleophilic addition of hydroxide ion to alkene
b) Protonation of alkene by electrophilic attack of $H_3O^{+}$
c) Electrophilic attack of $H_2O$ on carbanion
d) Nucleophilic attack of $H_2O$ on carbocation
e) Loss of $^{\ominus}OH$ to form an alcohol
f) Loss of $H^{\oplus}$ to form an alcohol

What is the product of the following reaction?

Bayer's reagent used to detect olefinic double bond is

$A$ dibromide $X$ $(C_4H_8Br_2)$ on dehydrohalogenation gave $Y$,which on reduction with $Z$ gave a non-polar isomer of $C_4H_8$. What are $X$ and $Z$ respectively?

$CH_2 = CH_2 \xrightarrow[KOH / H_2O]{KMnO_4} X$. The product $X$ in the above reaction is: