How to downgrade from Android 10?

Android 10 is extremely unstable on my Pixel XL. Most apps crashed within a few seconds after open, even including Google Play Store. That means, I could not do any new app install, because Google Play Store crashes within 3 seconds; I could not do any app update, because it crashes within 3 seconds. And the chat/phone call of Support function in Settings disappear. That means I have no more support. I could not take screenshot, because it crashes. Any idea how to downgrade from Android 10 without any data loss without any app reinstallation, just like the way we do the upgrade install (we do not need to do any backup)?