In the menu bar of Photoshop, under the 'Edit' header, you'll find an option for Keyboard shortcuts. Clicking this option opens an interface that allows you to fully customize hotkeys for all the toolbar options, as well as Application menus for everything in the menu bar.
You will be creating three hotkeys, using the three headings highlighted below.
1. Under the Image heading, scroll down until you find Image Rotation > Arbitrary. Set this to F1 and click Accept.
2. Under File, scroll down to Scripts > Browse. Set this to Alt+F1 and click Accept
3. Under Layers, scroll down to Flatten Image and set to Alt+F2