I believe that instructions sent to devices are placed in a queue and when a device checks in, the instruction is sent to it. https://learn.jamf.com/bundle/jamf-school-documentation/page/Quick_Action_Commands_for_Device_Management.html
With regards to updates, to force an update, you will need to clear the passcode for the device bearing in mind that the update is affected by battery percentage (has to be more than 50%), whether the power saving mode is on and in the case of a shared iPad, the user needs to be logged out. With regards to app updates, the app needs to be closed in order for the update to apply. Therefore it is a good idea in my mind to send a restart command to those devices that haven't updated their apps in a while to force an update of the app.