Where was the first republican system of the world during 6th century B.C. located?

By whom the first republic of the world was established in Vaishali –

In which century did the first Magadhan Empire rise?

Which Buddha text has described 16 Mahajanpads of 6th century B.C.?

Chand-Pradyota was the ruler of which ancient republic?

Which was the first capital of ancient Mahajanapada Magadh?