Do I have to fill out the whole application at once or can I pause and then come back to work on it later?

It is possible to complete the application in several sessions. However, within the application, individual sections have to be finished in one single session in order for the system to save your entries. In other words, you cannot pause and save in the middle of a section without having completed the required fields.
It is recommended that you hit “Save” regularly, ideally after completing all the mandatory fields within a section.
The system times out after 60 minutes, which means you lose any data you entered since the last time you clicked “Save”.