Break the spaghetti noodles and add it to the instant pot. Lay the noodles in a criss cross pattern (in opposite directions) as much as possible. This reduce the chance of noodles sticking togther once they are cooked.
Add the water and let the noodles soak in the water for about 5 minutes of time.
After about five minutes you may also use a fork to separate any noodles already stuck together (this will also help to prevent the noodles from sticking together or clumping). Doing this before cooking the spaghetti, reduces the chances of the noodles sticking together once its cooked.
Sprinkle salt, garlic and onion powders. Also add the butter and drizzle the olive oil across the noodles. Do not stir the noodles and make sure all the noodles is covered barely in water.
Close the instant pot with lid in sealing position. Press manual or pressure cook button and cook in high pressure for 3 minutes.
Once the instant pot has done the cooking and it beeps, press the keep warm/cancel button and wait for a natural pressure relase for about 12 minutes.
Once the pressure is naturally released for 12 minutes, carefully and gradually do a controlled manual release of remaining pressure. Once the pressure is all releaseed, carefully open the lid of the instant pot.
Stir the cooked noodles (in case the noodles tend to stick or clump a little, you may also add an extra spoon of olive oil and gently separate the noodles using a fork which will help), and add the sauce and cheese, stir well.
Use the saute option and heat the contents for few seconds so the cheese will nicely blend with sauce (make sure not to burn the pasta at the bottom of the pot). Finally add the milk (if you add early it may burn at the bottom of the pot), stir to combine and also sprinkle the oregano powder and the delicious instant pot spaghetti is ready to serve.
The spaghetti will absorb most of the sauce as it sits for a long time, so serve this hot as soon as you made if you like it saucy.