1 – Wrong
The enzyme is produced by the activation of the gene and not the internal temperature.
2 – Correct
The last line of the paragraph says that IF the cat had grown in a warmer temperature, the ears, front of the face, paws and tail would have been paler. 2 suggests that the temperature of those parts of the body were cooler than the rest of the body and hence, they are darker. So 2 is correct.
3 – Correct
Activation of the gene produces the enzyme which makes the coat colour pale. The environment causes the colour change in the ears, front of the face, paws and the tail.