Which of the following steps would be irrelevant while planning for a…

The correct answer is Option (2) → Emasculating the flowers

Dioecious plants bear male and female flowers on different plants (as in papaya), so every flower is unisexual. In artificial hybridisation, emasculation means removing the anthers from a bisexual flower bud so that the flower cannot pollinate itself.

Option (1) Dusting the pollen on the stigma — Incorrect. Dusting the chosen pollen on the stigma is the pollination step. It is needed in every cross, whether the flowers are bisexual or unisexual.

Option (2) Emasculating the flowers — Correct. A female flower of a dioecious plant has no anthers to remove. So emasculation is not needed; the female flower buds are only bagged before they open.

Option (3) Collecting the pollen — Incorrect. The pollen of the desired male parent must be collected so that it can be dusted on the stigma. This step is needed in all crosses.

Option (4) Bagging the female flower — Incorrect. The female flower bud is bagged before it opens to keep unwanted pollen away from the stigma. This step is still needed with dioecious plants.

NCERT Extract:
Pollination – “… If the female parent produces unisexual flowers, there is no need for emasculation. The female flower buds are bagged before the flowers open. When the stigma becomes receptive, pollination is carried out using the desired pollen and the flower rebagged.”
Pollination – “… In several species such as papaya, male and female flowers are present on different plants, that is each plant is either male or female (dioecy).”