Graceful Routing Engine Switchover (GRES) and Nonstop Active Routing (NSR) are two features used in Junos OS to provide high availability. GRES allows for the stateful failover of the Routing Engine, and NSR allows for the continuation of packet forwarding and protocol states during a Routing Engine switchover.
These technologies ensure that peer nodes are not alerted during a switchover. VRRP and ISSU serve different purposes and do not apply to this specific requirement.
References:
Juniper Networks documentation on High Availability: High Availability Features

https://www.juniper.net/documentation/en_US/junos/topics/concept/routing-protocol-is-is-security-designated-router-understanding.html#:~:text=If%20routers%20in
%20the%20network,a%20priority%20value%20of%2064.

The exhibit shows that the BGP session state is "Active," which generally indicates that the router is trying to establish a BGP session but has not received a response. One common cause for this issue is that there is no route to the BGP neighbor's address. Since the routers are using internal BGP (iBGP) and they are in the same AS, the AS number does not need to be unique, and a next-hop self policy is not strictly required for iBGP. The router-id is usually automatically determined and does not need to be explicitly set.
Reference:
Juniper Networks documentation on BGP: Troubleshooting BGP