Offline mode allows you to be out of internet signal and still be able to access information that was already available on the device and to complete a form.
To ensure that offline mode works at its best, make sure that the app is fully synced before going into offline mode. Ensuring all jobs, forms, contacts, accounts, etc are all up to date.
There are no limits to the number of forms you can complete in a single session. You can save all forms to be submitted later or when you go back to online mode. Forms will submit automatically upon submission.
There is no limit with regards to time when using an offline session but it would be advisable to sync or submit your forms as soon as you receive an internet connection.
Workflows will only work when online as it needs to retrieve triggers for it to progress your reports to the next stage. The same applies for form actions, the form needs to be submitted for the actions to be triggered. Same applies for Job Type communication through the stages of the job process.
The mud map is not dependent on having signal, this will work in offline mode.