Stable version released for Xiaomi 14 Ultra.
https://miuiver.com/tag/aurora-stable-rom/
Stable version not yet available for Xiaomi 13 Pro
https://miuiver.com/tag/nuwa-stable-rom/
Because the "change log" belongs to xiaomi. It usually contains security patches (unless it's a major update or a system vulnerability).
This is entirely your choice. If you have an unlocked bootloader, you are taking this risk.
The site is in Chinese. Use translation.
https://miuiver.com/
Gpay module is a module used for the device to pass the integrity test in google payments. From time to time google closes this vulnerability and developers update this module