Hi Praveen,
1- SAP MII Best Practice Guide for 12.x
2- Yes, definitely.
3- Please have a look at SAP MII Monitoring Services document: http://wiki.scn.sap.com/wiki/download/attachments/15603/SAP%20MII%20Monitoring.pdf?version=1&modificationDate=1337881502000&api=v2
4- Please have a look at SAP MII Enterprise Architecture section of the following "SAP Manufacturing Integration and Intelligence 12.X Best Practice Guide" document: SAP MII Best Practice Guide for 12.x
5- While some of the customers prefer SAP PI + MII integration for advanced monitoring and centralization purposes for more than a few assets, I would say that the scenarios without SAP PI are a bit more smooth (from MII standpoint of view) and obviously requires less build and maintenance effort. However, it all depends on your needs. If you have a large landscape with a lot of different SAP ERP - SAP MII integrations you may consider having a PI between them. More information on: SAP Manufacturing Implementation Architecture
BR,
Alper Somuncu