To isolate management traffic in a non-default routing-instance on Junos-based devices, you can use the set system management-instance and set routing-instances mgmt_junos commands. set system management-instance: This command associates the management interface (usually named fxp0 or em0 for Junos OS, or re0:mgmt-* or re1:mgmt-* for Junos OS Evolved) with the non- default virtual routing and forwarding (VRF) instance. After you configure the non-default management VRF instance, management traffic no longer has to share a routing table with other control traffic or protocol traffic.
set routing-instances mgmt_junos: This command creates a new routing instance named mgmt_junos. The name of the dedicated management VRF instance is reserved and hardcoded as mgmt_junos; you cannot configure any other routing instance by the name mgmt_junos.
Therefore, options C and D are correct. Options A and B are not correct because they attempt to assign an interface to the mgmt_junos routing instance, which is not necessary for isolating management traffic.

A is correct because you need to configure BGP multihop to enable redundancy for the EBGP peering between the two routers. BGP multihop is a feature that allows BGP peers to establish a session over multiple hops, instead of requiring them to be directly connected. By default, EBGP peers use a time-to-live (TTL) value of 1 for their packets, which means that they can only reach adjacent neighbors. However, if you configure BGP multihop with a higher TTL value, you can allow EBGP peers to communicate over multiple routers in between. This can provide redundancy in case of a link failure or a router failure between the EBGP peers.
B is correct because you need to configure loopback interface peering to enable redundancy for the EBGP peering between the two routers. Loopback interface peering is a technique that uses loopback interfaces as the source and destination addresses for BGP sessions, instead of physical interfaces. Loopback interfaces are virtual interfaces that are always up and reachable as long as the router is operational. By using loopback interface peering, you can avoid the dependency on a single physical interface or link for the BGP session, and use multiple paths to reach the loopback address of the peer. This can provide redundancy and load balancing for the EBGP peering.
C is correct because you need to configure routes for the peer loopback interface IP addresses to enable redundancy for the EBGP peering between the two routers. Routes for the peer loopback interface IP addresses are necessary to ensure that the routers can reach each other's loopback addresses over multiple hops. You can use static routes or dynamic routing protocols to advertise and learn the routes for the peer loopback interface IP addresses. Without these routes, the routers will not be able to establish or maintain the BGP session using their loopback interfaces.