Didn't have time to test it. But, it seems that there is some kind of EIS stabilization for video on all resolutions. I can cleary notice it @2k, and maybe even 4k. It's not as effective @2k as at HD obviously. And separate settings for EIS under HD resolution disappeared,
No, i think if its present on the Huawei update cloud, like: ht tp://update.hicloud.com:8180/TDS/data/files/p3/s15/G3409/g1699/vXXXXXXX/f1/full/CLT-L29_hw_eu/update_full_CLT-L29_hw_eu.zip vXXXXXXX is the version number, G3409 and f1699 is the current place for the 9th version, other CUST too. You can curl it from version x to y. I do it, but unavailable...I think if I didn't miss anything..
Yes, the bootloader (xloader) will be updated, there's no way around it. Yes, downgrading works, but you will have to factory reset after downgrading.