Export from 2 factories

Dear Members, I need clarification on excise matter for the following situation. 1. We are manufacturer exporter based out of UP and have an export order. 2. The product is such that major parts will be manufactured by us in our factory. 3. Some parts are bought out(from manufacturer in Mumbai) which need to be exported 'as it is' and do not need any manufacturing to be done. In other words, the parts from our factory and manufacturer in Mumbai will be exported in dismantled condition. I need advice on following doubts; a. Can I get the parts from Mumbai manufacturer in our factory in UP for trial purpose without payment of excise and sales tax? If yes, is it necessary to return the parts back to Mumbai manufacturer? b. As the final export documents (commercial invoice, packing list etc.) will be made by us, can we export in 2 lots - one from ICD Delhi and other parts from JNPT? In this case, export from our factory will be as manufacturer exporter and against ARE1 and we will be merchant exporter for export from Mumbai manufacturer. c. As merchant exporter, is the CT1 bond to be submitted by us in central excise of our jurisdiction in UP and then submit the CT1 certificate to the manufacturer in Mumbai? AM I right in saying this? Hence, excise duty will be NIL when Mumbai manufacturer makes invoice on us. d. We submit H form to Mumbai manufacturer against proof of export so that Mumbai manufacturer will invoice us with NIL Sales tax. e. Lastly, if we decide to ship as one consignment by bringing the parts from Mumbai factory to our factory, how to avoid payment of excise duty and sales tax to Mumbai supplier? Sorry for the lengthy post and thanks in advance for a detailed and clear reply.