Golden age of reptiles is

Which of the following is correctly matched w.r.t. era and its period?

Amphibia first appeared in which of the following period?

The first cellular form of life could have originated

The first mammals were like ...$A$... Their fossils are small sized. Mammals were ...$B$... and protected their unborn young inside the mother's body

Choose the correct option for $A$ and $B$ to complete the given $NCERT$ statement