Preheat oven to 325°F. Line the bottom of a 9-inch springform pan with parchment paper, lightly grease the sides, and wrap the outside tightly with two layers of heavy-duty foil.
In a medium bowl, combine graham cracker crumbs and sugar. Pour in melted butter and stir until the mixture resembles wet sand. Press firmly into the bottom and about 1 inch up the sides of the prepared pan. Bake for 10 minutes, then set aside to cool.
In a stand mixer fitted with the paddle attachment, beat softened cream cheese on medium speed for about 2 minutes until completely smooth. Scrape down the bowl as needed.
Add sugar and flour to the cream cheese, mixing on medium-low speed until combined. Add sour cream, vanilla extract, and almond extract, and mix until smooth.
With the mixer on the lowest speed, add eggs one at a time, mixing only until the yellow disappears after each addition. Do not overmix. Fold in rainbow jimmies sprinkles with a rubber spatula.
Pour the filling over the pre-baked crust and tap the pan gently on the counter to release air bubbles. Place the pan in a roasting pan and pour hot water into the roasting pan to reach 1 inch up the sides of the springform pan.
Bake for 70-80 minutes until the edges are set and the center 2-3 inches jiggles like firm Jell-O. Do not open the oven door during the first 60 minutes.
Turn off the oven and leave the cheesecake inside with the door propped open 1 inch for 1 hour. Then remove from the water bath, peel off the foil, and let cool completely on a wire rack for another 1-2 hours.
Cover loosely with plastic wrap and refrigerate for at least 6 hours or overnight to fully set.
Beat cold heavy cream with powdered sugar and vanilla extract until stiff peaks form. Pipe or spoon onto the chilled cheesecake and top with additional rainbow sprinkles.
Run a thin knife around the inside edge of the pan, release the ring, and slice with a hot, dry knife between each cut.