Need help with updating disconnected devices

hey, I am new to azure and IOT and I need help with knowing how to do this. The scenario is that: I have a set of Linux devices that can't be connected to the internet ever, these devices should be connected to another device (will have internet) which will act as parent to all these disconnected devices. The challenge is to update these child devices using Azure IOT, the updates will be deployed in the hub, and it has to passed to child devices via parent device and automatically needs to be installed in the child devices. The parent might not require this update or might. How will I do this? also I can't use any scripting mechanisms.

Now when I surfed a bit through azure documentation, I found out that I can use device update for this, What I found was:
1) setup every device in IOT hub 

2)set the device with internet as parent and others a child

3)set up MCC module in parent 

4)Connect the devices physically (Lan or Wi-Fi)

5)Roll out updates

Now I don't know whether this is true or not, it's just my understanding. I am having few doubts:

1)do we also add the child devices (disconnected devices in IOT hub), if yes what if we have 1000 devices? (I'm asking about scalability)

2)How do I actually physically connect the parent and child devices, do I just plug in Lan/Wi-Fi, or do I have to do anything else?

3)How to add MCC Module?

4)how does this actually works? is it feasible?