The procedure to create PR is according to the safety stock mentioned for the material or can be triggered from a requirement. For creating a PO, you need to have the scheduling agreement in place .After the MRP is run the schedule lines are generated which is nothing but the PO.

Special Stocks that are available are Subcontracting, consignments, pipeline, project, sales order, RTP, stock transfer, and the third party.

No, it is not possible to have scales in a quotation

The steps that are involved in consignment cycle is by creating consignment info record with proper tax code, maintain output condition record for KONS, no invoice verification done, create Po with item category K, process GR, but settlement is done through MRKO transaction.

Scales are to fix a price in the info record for a quantity from 1-100 price Rs.150 and if the order quantity is 101- 500 the prices is 140. Scales cannot be used directly in PO but can be pulled into the PO from various master data like info record, quota arrangement.

The Contract agreement or the Outline Agreement is that create the centrally contract (cross-plant) where it can maintain different pricing conditions for each and every plant. It creates the Release Order with reference to Outline Agreement. No detailed delivery schedule can be made in the Release Order. No Release documentation is created. Only time-dependent conditions can be created, Some Item Category 'M' and 'W' can be used. 
Whereas the Scheduling Agreement is the Plant Location what must be entered in the Scheduling Agreement. Its no need to create any other purchasing document except for delivery schedule line via Transaction ME38 or MRP running (with the appropriate setting of Source List). Delivery Schedule line items are created subject to your specific requirement. It can create both Scheduling Agreement with or without release of Documentation (subject to the Document Type LP or LPA) with the selection of either FRC or JIT delivery schedule. Either time-dependent or time-independent conditions can be created subject to the customizing in the Document Type of the Scheduling Agreement. Item Category 'M' and 'W' can not be used.

The release procedure with classification deals with the purchase requisition it can be released both at item level and at the header level. Coming to release procedure without classification can also be used for purchase requisition which is used for item level release only. All other external documents cannot be released with classification. These two procedures are mutually exclusive to say, it has to be decided in favor of one of them only.

The Byproducts take care of subcontracting in BOM for the header.

The procedure to give specifications are normally prepared for the business requirement document in which we specify what is required, what field and tables have to be referred for the required development.