Form-h

Dears Please clarify my doubts. X Ltd (Manufacturer,Tamilnadu), Y Ltd (Buyer,Maharashtra), Z Ltd (Third party, USA). X Ltd sold goods to Y Ltd against CT-1 and Form-C. Y Ltd PO showing they are Export to Z Ltd(USA). in this situation Y Ltd issue CT-1 and Excise Duty will not be applicable ED=0 My Doubts 1) Y Ltd issue CT-1, Whether Y Ltd should be Export the purchased goods from X Ltd. or can use other? 2) if buyer issuing CT-1 whether they should issue Form-H for CST Purpose? 3) if buyer issue CT-1 and Form-C also , whether this transaction is correct?