Yes, if you intend using them as wireless access points/ethernet switches. Give each a different IP address outside of the DHCP range of the master hub, disable DHCP on the slaves and connect them LAN port to LAN port
Yes, you can set them up as Access Points to boost your Wi-Fi around your house. You will have to plug them into ethernet though. There is a guide on Google about how to do it, just search 'setup bt hub 5 as access point'. Don't think I can post the link.
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