Which of the following statements is incorrect regarding the Bhopal gas tragedy?

Consider the following reasons for the massive fish mortality observed in a lake near a village within a few days:
$(1)$ Excessive use of urea and phosphate fertilizers in nearby crops.
$(2)$ Spraying of $DDT$ using aircraft.
$(3)$ The lake water turned green and foul-smelling.
$(4)$ Initial decrease in phytoplankton in the lake leads to a maximum decrease in photosynthesis.
Which of the above reasons are responsible for the massive fish mortality?

The Wildlife Protection Act was introduced in:

Which of the following statements is incorrect?

$A$: Polyblend is a fine powder of recycled modified plastic.
$R$: The blend of polyblend and bitumen helps to increase road life by a factor of three.

Identify the correct statements from the following:
$(i)$ $DDT$ is non-biodegradable.
$(ii)$ Heavy metals are responsible for biomagnification.
$(iii)$ High concentration of $DDT$ disturbs calcium metabolism in birds.
$(iv)$ The concentration of $DDT$ in large fish can be up to $2 \, ppm$.