Fail-open is a feature that allows traffic to pass through the IPS sensor without inspection when the sensor fails or is overloaded. If fail-open is set to disable, traffic will be dropped in such scenarios1. References:
= IPS | FortiGate / FortiOS 7.2.3 - Fortinet Documentation
When IPS (Intrusion Prevention System) is configured, iffail-openis set to disable, it means that if the IPS engine fails, traffic will not be allowed to pass through, which can result in traffic being dropped (D). This is in contrast to a fail-open setting, which would allow traffic to bypass the IPS engine if it is not operational.

The commands that start with the # sign did not run because they are treated as comments in the CLI script. Incomplete commands can cause CLI scripts to fail because they are not recognized by the FortiGate device. The other options are incorrect because static routes can be added using CLI or GUI, and CLI scripts do not need to start with #!. Reference := Configuring custom scripts | FortiManager 7.2.0 - Fortinet Documentation, section "CLI script syntax".

IKE version 2 supports the extensible authentication protocol (EAP), which allows for more flexible and secure authentication methods1. IKE version 2 also exchanges a minimum of four messages to establish a secure tunnel, which is more efficient than IKE version 12. Reference: = IKE settings | FortiClient 7.2.2 - Fortinet Documentation, Technical Tip: How to configure IKE version 1 or 2 ... - Fortinet Community

To reduce the number of BGP sessions in an IBGP network, you can use a route reflector, which acts as a focal point for IBGP sessions and readvertises the prefixes to all other peers. To configure a route reflector, you need to enable the route-reflector-client option on the neighbor-group settings of the hub device. This will make the hub device act as a route reflector server and the other devices as route reflector clients. References := Route exchange | FortiGate / FortiOS 7.2.0 - Fortinet Documentation

In an ADVPN scenario, when traffic is initiated from a client behind one spoke to another spoke, the hub sends a shortcut query to the initiating spoke. This query is used to determine if there is a more direct path for the traffic, which can then trigger the establishment of a dynamic tunnel between the spokes.