Can I get my data out?
Yes. An owner can download everything at any time, even when the business is locked or closed.
Yes. Your data is yours. An owner downloads it from Settings, Export: everything at once as one zip file, with a spreadsheet for each kind of record and every file you stored, or one kind at a time as a CSV file. This works even when the business is locked or closed. See Export your data.
If you stop trading, an owner can close the business. For 90 days you can still download everything or reopen it; after that it is deleted for good. See Close your business.