BTHybrid Connect 4G Backup for BT Smart Hub 2 ONLY up to 30MBPs Backup Link to BT Broadband

How long does it take to switch from the regular bt wifi to this? would it interrupt a video call?

Can this just plug into bt smart hub 2 and work or do you need to still pay bt the £7 per month subscription for it to work?

Do u have to use an ee sim in this or will any sim work? also dose it have to be connected to a by router or can i use my own?

If hybrid connect has an ee sim installed and is connected to bt sh2, does sh2 need a bt contract / broadband for the hybrid connect to work 4g ?