Row Material sent for jobwork to other state

my client "A" (registered at Mumbai) import rough diamonds and sent said rough diamonds (raw material) for processing(cutting &polishing work) on jobwork to "B" at Surat(Gujarat) my query as under:

1) "A" sent said rawmaterial on Delivery Challan / or Tax Invoice ?

2) "A" liable to charges IGST on said rawmaterial sent to "B" for jobwork?

3) if "A" liable to charged IGST on said rowmaterial value than after when "B" return said finished goods(cut & Polished Diamonds) to "A", he will charges IGST on which amount? ( GST on finished goods @ 3% & GST on jobwork @ 5%)