Yes, Saibya is one of the Queens of Lord Krishna. This is confirmed in Bhagavat Purana Canto 10, Chapter 83, Text number 6.
Yes
In the Bhagavat Purana Saibya is a proper name for one of Lord Krishna's wives, also one of His horses in Dvaraka Pastimes was named Saibya. The Vaisnava Tosani names one of the gopis as Saibya.
Yes
anupama
The names of Lord Krishna's chariot horses are: Saibya, Meghapuspa, Balahaka, and Sugriva Reference: Bhagavat Purana 10.53.5
no.
Yes
yes
yes
yes
Meera praised passionately Lord Krishna.
Lord krishna was born before 1st century in gokul