Does Realme X has fingerprint scanner?

No. Realme X does not have the image stabilization support. 

Yes, Realme X is a dual 4G with VoLTE mobile. You can use 2 sim cards on 4G networks at the same time. 

Yes, Realme X does have the Dolby ATMOS support. It is enabled by default. 

No. Realme X does not have the notification light but it does have the Always-On display - so you can get notifications via it.