In sap business one can i maintain auto batch costing if so how can i maintain batch costing for multiple item

What is manual and backflush in Production and in which scenario used .. with example will be helpful

Can autobatch be triggered automatically without manual entry in the time of AP and AR invoice in SAP B1.. In trading segment

Need to know if the purchase price changes from vendor can we have option in sap b1 to select in po time ,last price and current price of a particular item. Also the approval shud go to the department if any selection user does .