No. Huawei does not provide a download portal for router firmware for the H122-373. You must rely on community archives, which is why verifying the file hash (MD5/SHA) is crucial if you find one.
A: Downgrading is blocked by Huawei’s rollback protection. You cannot go from SP2 to SP1. This firmware is for users on SP1 (base) or older (SP31, SP40). huawei h122373 firmware 10051h612sp1c00 universal link
The firmware version 10.0.5.1(H612SP1C00) refers to a specific system software for the Huawei 5G CPE Pro 2 (H122-373) huawei h122373 firmware 10051h612sp1c00 universal link