Soft Delete- You are logically deleting data, means keeping data within DB and only changing a flag which will represent whether data is active or not. Hard Delete- Data is physically deleted from the database table. It will not be available to any of the user.
The alternate flow is a sequence of actions, different from the basic flow, which still delivers the desired result to a customer. The exception flow are any actions that will cause the user to not achieve the desired result.