Explanation
According to the FortiManager Administration Guide1, "FortiManager obtains the FortiSwitch status information by querying the FortiGate REST API every three minutes." Therefore, option B is true because it describes how FortiManager gets the information about the managed switches. According to the same guide2,
"If you make any changes in this module, you must install them on your managed device so that they are applied on your managed switches." Therefore, option C is true because it describes what the administrator must do after making any changes on FortiSwitch manager. Option A is false because central management is the default management mode on FortiManager, not per-device management. Option D is false because anyswitch discovered or authorized on FortiGate will be automatically added on FortiSwitch manager, not manually.
1: https://docs.fortinet.com/document/fortimanager/7.0.0/administration-guide/734537/fortiswitch-manager 2:
https://docs.fortinet.com/document/fortimanager/7.0.0/administration-guide/734537/fortiswitch-manager#fortisw

Explanation
According to the FortiAuthenticator Administration Guide2, "The guest portal provides pre and post-log in services for users (such as password reset and token registration abilities), and rules and replacement messages can be configured." Therefore, option C is true. The same guide also states that "Administrators can use one or more incoming parameters to configure a mapping rule for the guest portal." Therefore, option D is true.
Option A is false because remote users can sponsor any number of guest accounts, as long as they do not exceed the maximum number of guest accounts allowed by the license. Option B is false because administrators can choose to approve or reject guest accounts, or enable auto-approval.