Starting with hot water will mean the pot will get up to pressure sooner. And the sooner the pot gets to pressure the sooner it can start "cooking", which will reduce the cooking time.
Set to cook at high pressure That is all you need. If using frozen chicken, adjust to 15 minutes.
Using natural release is the key to this recipe. The remaining pressure will continue cooking the chicken and rice for 25 minutes.
Do not be tempted to use "quick release" as the starch from the rice will spill everywhere and you'll of course end up with an uncooked porridge.
Substitute chicken with mushrooms like shitake, portobello, and button mushrooms. For extra protein, add diced firm tofu after pressure cooking. Cook for 1 to 2 minutes then turn off the instant pot.