No, SRAM RED, Force, and Rival eTap AXS are not backward compatible with SRAM RED eTap 11-speed. The AXS Mobile App and companion parts require a Bluetooth connection. The SRAM RED eTap 11-speed system is not able to communicate to the SRAM Mobile App as it is not Bluetooth enabled. Similarly, SRAM RED eTap 11-speed is not able to communicate to the 12-speed AXS components, as they communicate through a different version of our super secure proprietary wireless protocol.
Historically when upgrading groupsets, most components have not been compatible with other gear ranges due to the following drivetrain changes: chainring width, chain width, chain roller size, cassette cog spacing, freehub body compatibility change for mechanical groups. While we are used to firmware upgrades to other types of electronics operating systems, there are other factors at play with previous generation bicycle parts that do not allow for compatibility to the newest systems, much like mechanical drivetrains. In this same way, 11-speed parts are not compatible with 12-speed parts of AXS drivetrains.