How to study Life Cycle of Tailed Jay butterfly

It was found that Butterfly is doing something on the leaves of a plant by @Theertha. Two eggs were found on false Ashoka leaves by @Theertha on 26th August, 2023 The butterfly was green and black in color, it was like Tailed Jay. She also confirmed that false Ashoka is host plant for Tailed Jay, so eggs were of Tailed Jay butterfly. On 29th August, 2023 these eggs became caterpillar.
The colour of caterpillar was black and white. On 05th September, 2023 the caterpillar turned to green and yellow in color. On 20th September, 2023 one caterpillar became pupae. The second caterpillar is still not pupae, so it was argued how much time will other caterpillar take to become pupae? @Theertha said that other caterpillar will take double the number of days than first caterpillar to become pupae. Is it possible that 100% difference can occur? Can human pregnancy take 9 months in one case and 18 months in other? The difference can be of some days/some percentage but not so huge difference as the enzymes will fuction more or less same way in biology in eggs of same mother butterfly.