Spray a 7-inch springform pan with nonstick cooking spray. Line the bottom of the springform pan with parchment paper, if desired. Set aside.
Place Oreos into a large zip top bag. Press as you seal to remove as much air as possible from the bag. Use a rolling pin and crush the Oreos into crumbs.
Pour the Oreo crumbs into a medium bowl. Add the melted butter to the Oreos and mix until combined.
Press the Oreo mixture into the bottom of the prepared 7-inch springform pan. Place into the freezer for 10 minutes.
Oreo Cheesecake Filling
Mix together the cream cheese, condensed milk, sugar, and cornstarch until well blended with an electric mixer. Add eggs, one at a time, and beat well. Add lemon juice and vanilla extract until well blended. Add sour cream and beat for 1 more minute.
Pour the cheesecake filling over the crust into the springform pan.
Pour a cup of water into the bottom of the Instant Pot pot. Arrange the springform pan onto the trivet and lower into the Instant Pot pot.
Secure the lid to the Instant Pot. Set the timer for 25 minutes at High pressure. Allow the pressure to release naturally for 10 minutes and then carefully quick-release the remaining pressure.
Carefully remove the lid to the Instant Pot. Using the handles of the trivet, lift the cheesecake from the Instant Pot pot. The cheesecake will have risen considerably, but will reduce as it cools.
Allow the Oreo cheesecake to cool on the trivet, then release the sides of the springform pan and carefully remove the cheesecake from the pan, cover well with wrap and refrigerate until chilled completely, about 4 hours.
Remove the cheesecake from the refrigerator and remove the sides of the springform pan.
Top the cheesecake with whipped cream and crumbled Oreo cookies for serving.