There is no standard integration of Projects and Sale Order.
In Project Management you can create workplan and create deliverables for the tasks. Deliverables listed on a task must be completed for the task to be completed.
You can associate billing, shipping or procurement integration to deliverables. When you assign a shipping action to a deliverable item, system will allow you to interface demand from the PJT to a the Planing application (MRP / APS). When you assign a procurement action type to a deliverable, system will allow you to interface an approved requisition to the procurement application. With Shipping integration you will be able to send a shipping request from the PJT into the shipping application, so item can be picked and shipped to the requested customer or project location. Integration with planning and shipping depends on enableing Project Manufacturing, assuming you will need to manufacture or assemble the requested inventory item.
To enable Deliverable's for Sales Order / PO related requests you need to have Project Contracts (OKE) in place.
You question had two parts:
1. Project Integration with Sales order via Deliverable - As mentioned by Dina, the linkage via deliverables doesn't directly create a sales order in Order Management by triggering a request from projects module. But a demand can be initiated and same can be linked to a MDS and tracked till the item is shipped.
2. So only after this task completes the nest task can start. - This can be achieved using task dependencies. Define dependency as Finish to Start so that, the dependent task cannot be started unless this task is marked as COMPLETED as illustrated below:
Finish to Start
Predecessor must finish before Successor can start. [Land must be purchased before road building can start]
Hope it helped.