The two configuration settings that are global settings are:
C. HA settings - High Availability settings are typically configured globally to manage failover and redundancy.
D. FortiGuard settings - FortiGuard settings for security services and updates are also configured globally to ensure consistent protection across the network.
HA configuration overview. The purpose of an HA configuration is to reduce downtime when a zone or instance becomes unavailable. This might happen during a zonal outage, or when an instance runs out of memory. With HA, your data continues to be available to client applications.
FortiGuard > Settings provides a central location for configuring and enabling your FortiManager system's built-in FDS as an FDN override server.

C because it exceeded the Extreme memory threshold.
"However, if the memory usage exceeds the extreme threshold, new sessions are ALWAYS DROPPED, regardless of the FortiGate configuration." if the memory usage keeps increasing, it might exceed the extreme threshold. While the memory usage is above this highest threshold, all new sessions are dropped.
Note: "Extreme threshold is when the memory usage goes above 95%, and all NEW sessions are dropped.

*> mean active routes
first square bracked mean administrative distance
second bracket square mean priority (valid only on static routes) metric applies only in multiroutes with same administrative distance.

FortiGate performs route lookup based on the trust packet. The trust packet is the first packet of the session that is sent by the session originator.
This is the packet that initiates the communication. The route lookup is also done on the trust reply packet, which is the first reply packet received from the responder.
In summary, FortiGate looks at the initial packet from the session originator and the first reply packet from the responder when performing route lookup to determine the suitable gateway.