Importing Prepayment invoices and their allocation to Invoices in AP

Dear All

We have a requirement where we want to release some advance payment to our suppliers based on approved PO in an external third party application. My query is as below:-

1) Can we import invoice type "PREPAYMENT" automatically through AP open interface ?

2) Can we import invoice type "PREPAYMENT" automatically through AP open interface as paid invoices ?

3) Can we allocate prepayment invoices automatically to a standard invoice ?

4) Is there any API to create PREPAYMNET invoice automatically through some staging table ?

Thanks In advance . We are at R12.1.3.

Thanks

Pawan