If you do not hide the activity restriction they should be able to see the "rules".
I hide all of my activity restrictions, as it was confusing for some of the students. I place my course instructions in the Course Detail Page.
To pass this course, you must post/reply to three forum discussions and post one new discussion.
You can show the activity conditions if you don't hide it, also, it's recommended to post course instruction in a page module in the top section, so students will know what they need to do with each activity.
It depends on your moodle version. The conditions were not displayed anywhere prior to moodle 3.11; back in the days it was just the good old checkbox. Something lots of people miss badly.
So if you want them to be displayed, and you’re on an older version of moodle, you either need to upgrade or manually write that information into the description of the activity.
If you are on 3.11, check the the course settings page, under the completion tracking section there’s a setting to show or hide the conditions.