You can set in which order tasks must be completed for a checklist in each template. There are two supported properties, Unordered and Ordered.
Unordered is the default for all new templates and means that tasks can be marked as completed in any order.
Ordered means that tasks must be completed from top to bottom in a checklist. You can not complete a task if not the previous task has been marked as completed.
To set task completion order you open the template and click on Set task properties in the action menu.
This will display the two possible task order properties, where the currently used is marked as selected with a blue icon. To change task order click on the property currently not marked as selected.