display condition

Some time ago, I've set a widget for showing the most active users, but I want this to be seen by logged-in users only. So I set the display condition to be $xf.visitor.user_id but today I realized that only admins can see it. Could anyone help me understand what is going on? Is there any...

I want to embed som Google calendars, but they are not responsive, so I think it is best to embed smaller calendars in widgets only shown on small screens. Can I make som display condition, so some widgets are only shown only smaller screens?

Is there a display condition to show a widget in only one particular style?

I want a sidebar widget to be visible when viewing threads in a particular forum. Using the Display Condition field, I would expect this to show the widget in threads with a node_id of 358: $context.thread.node_id == 358 ...but that does not work and the widget never displays. Using an HTML...