1 what is the difference between the transactions display current and display at key date?

The difference connecting the transactions Display Current and Display at Key Date is that the materials like trading and finished goods, but also services are time-dependent master data in the SAP system, it means changes can be accurately recorded and tracked over time

Display current represents the prevailing state of the material. The initial screen for transaction Display at Key Date cause a user to access a key date in addition to the material number.