At which stage did the artist work on portraits during the book paint…

The correct answer is Option 2- Chiharanama

Most of the paintings that we see as Mughal miniatures were parts of manuscripts and royal albums, i.e., the visual and text shared space in a given format. For making book painting, the following process was adopted. Sheets of handmade paper were prepared and cut to suit the size of the manuscript. Designated space was left for the artist to fill it with a suitable visual composition. Then, the pages were ruled and filled with text. Once the text was written, it was given to the artist, who would compose a synoptic visual representation of the text. The artist would begin from the stage of making the composition, i.e., tarh, to portraits, i.e., chiharanama to the final stage of colouring, i.e., rangamizi.