Incase you need to check the consignment (vendor) stock, you can get the same from T-code MB52 and select the Special stock indicator 'K' for viewing the vendor stock. For viewing your own stock received from a particular vendor, you can get the same by T-code MB51, mention the vendor number and the movement type 101 (GR goods receipt) i.e. all goods receipt against purchase order.
1)You can get the details from ME2L,ME2M,ME2M.
Better to use ME2N as PO number will be the input field and Under Order Quantity column you will get Order quantity, under Still to be delivered quantity will give you quantity to be delivered.
2) With the help of your ABAP er you can also create z report by making use of tables EKPO ans EKBE