Two very basic question on DHCP relay agent?

Hi guys, again inquiring about DHCP (sorry !). Just to confirm and freshen up some concepts before final approval from management. I just had two very fundamental questions on DHCP Relay agent.

1. DHCP relay has to be configured if DHCP server and DHCP clients are on a different subnet. But if there are more than routers on the path between DHCP clients and DHCP server, do we have to configure DHCP relay in every hop? Or do we configure DHCP relay in only the router on the same subnet as that particular DHCP client?
   Please refer to the this image, do we have to enable DHCP relay in router 2 and router 3 ? My understanding is, router 1, if configured with DHCP relay, will convert DHCP Discover and Request broadcast packets to unicast to DHCP server, so no need to enable next hop routers as the messages are already unicast. I just wanted to double check.
2. Which interface do we configure the DHCP relay in router ? The interface directed to the DHCP client (downlink interface / southbound interface ?) or the interface directed to DHCP server (upllink or the northbound interface)?
   Please refer to this image, I think it's the interface directed to the DHCP client. Again I just need to double check.
   

Like I said, just needed to double check before preparing the final design. Thank you everyone in advance.