Here's how to stop users from submitting incomplete audits or observations.
Go To Settings > Modules > Audits OR Observations (whichever you’d like this restriction for)
Click on the workflow LINK between workflow steps 1 & 2 (or any workflow links that you’d like to block it for.
3. Click the [Add Rule Restrictions] button underneath the 'Restrict State Change To' heading
4. Set the rule to "Answers Completed" > "Equal" > "True" and click update.
And you're done! Now a user that hasn't completed their checklist won't be ablet to advance between those two workflow steps.