Is actual possession by the second manufacturer of the item produced required before its delivery to the customer in parallel istisna' (manufacturing contract), and is it permissible for parallel istisna' to involve three or more manufacturers?

In the Istisna' (manufacturing contract), constructive possession is permissible by enabling the manufacturer to deliver the manufactured item to the commissioning party after its completion. By this, the manufacturer's liability ends, and the commissioning party's liability begins. If constructive possession takes place and liability transfers to the first commissioning party, then he may deliver it to the customer. There is no specific number of commissioning parties, but it is not permissible to sell the manufactured item before possessing it, either actually or constructively, nor to link Istisna' contracts to each other. Each manufacturer must bear the responsibilities of their contract and guarantee the manufactured item before delivering it to the commissioning party. The institution is not permitted to transfer its obligations with the client to the manufacturer in a parallel Istisna' contract.