1. Does Qualcomm Centriq 2400 have sve instruction set? The 2400 is armv8.a.
2. how to know whether an arm cpu support sve instruction set?
3. After which year, does arm cpu support sve instruction set?
Again, for specific details of specific manufacturer's implementations, you need to ask the manufacturer!
The ARM document tells you that SVE is optional - so only the specific manufacturer can tell you whether they implemented that option in their particular product!