Can I just flash firmware but not FS?

[senter]

Hmmn so I see it as :Asian Pacific languages (Chinese simplified, Indonesian, Malay, Philippine-Tagalog, Vietnamese) No good to me tbh.

So would this work?
CID53:
K770_R8BC004_MAIN_GENERIC_VI_RED53
K770_R8BC004_FS_TAIWAN_RED53
HB1-06_Gen_CDA102568_105_R8A_GENERIC_TAIWAN

CID52:
K770_R8BC004_MAIN_HONG_KONG_VI_RED52 or K770_R8BC004_MAIN_GENERIC_VI_RED52
K770_R8BC004_FS_HONG_KONG_RED52
HB1-06_Gen_CDA102568_104_R8A_GENERIC_HONG_KONG

Sadly theres no HK CID53 firmwares for K770i. I heard from somewhere the Cust pack must match the FS, what does that mean?

Each File System is different and is designed for different regions.
Custom pack contains the required settings for the File System.
If you use different version File System and Custom pack - flash program (XS + +) will give you an error.
Because languages do not match, settings, etc. for the region - must use the same version to match your settings, languages, etc.
In branded versions can use different custom pack, but it should be checked for which regions is designed File System.