What is the product formed when ethylene reacts with $1\%$ cold alkaline $KMnO_4$?

The decreasing order of reactivity of the following alkenes towards $HBr$ addition is:
$(I) \ CH_3-CH=CH_2$
$(II) \ CF_3-CH=CH_2$
$(III) \ MeOCH=CH_2$
$(IV) \ CH_3-CO-CH=CH_2$

Which of the following alkenes will yield $2-$methyl propanal on reductive ozonolysis (addition with ozone followed by the reaction with $Zn / H_2 O$)?

Predict the major product formed when $HCl$ is added to $2-$methylprop$-1-$ene $(isobutylene)$. Explain the mechanism involved.

Addition of $HCl$ to propene in the presence of peroxides gives:

Which of the following reactions does not involve a carbocation as an intermediate?