Enabling Quiesce Mode in the Unified Access Gateway (UAG) Admin UI is the recommended approach for minimizing downtime during maintenance or upgrades when the UAG is part of a load-balanced cluster.
Quiesce Mode allows the UAG to stop accepting new connections while allowing existing sessions to continue until they naturally end. This ensures minimal disruption to users and allows for a controlled upgrade process.

Explanation
One of the benefits of using virtual machines is that they are independent of physical hardware. This means that they can run on any compatible host machine, regardless of the underlying hardware components. This also enables them to be migrated, moved, or copied easily from one host to another, without requiring any reconfiguration or installation. This enhances the flexibility and portability of virtual machines, as well as their availability and disaster recovery.
Another benefit of using virtual machines is that they are faster to provision than physical machines. This is because they can be created from templates or snapshots, which contain preconfigured operating systems and applications. This reduces the time and effort needed to install and configure software on each machine.
Moreover, virtual machines can be cloned or duplicated quickly, allowing for rapid scaling and deployment of multiple identical instances.
References :=
Virtual Machines Overview
Creating and Provisioning Virtual Machines
Migrating Virtual Machines

Explanation
Roles and permissions are a way of controlling the access and actions of administrators and users in Horizon.
By default, Horizon provides two predefined roles: Administrators and Read Only Administrators. However, a high-level administrator can create custom roles with specific privileges to suit different needs and scenarios.
To create a custom role, the administrator needs to follow these steps:
In the navigation pane under the Settings section, click on Administrators > Roles and Permissions.
In the Roles and Permissions page, click on Add.
In the Add Role pane, enter a name for the role in the Role Name text box.
In the Privileges section, select the checkboxes for the privileges that you want to assign to the role. You can expand or collapse the categories to view or hide the sub-privileges. You can also use the Select All or Deselect All buttons to select or clear all the privileges in a category.
Click on Save to create the custom role.
The custom role will appear in the Roles and Permissions page, where you can edit or delete it as needed. You can also assign the custom role to users or groups in the Users and Groups page. References: [Create Custom Roles] and [VMware Horizon 8.x Professional Course]

Explanation

The default URL used to access the Horizon Console is https://<connection_server_FQDN>/admin, where
<connection_server_FQDN> is the fully qualified domain name of the Connection Server instance. This URL allows you to log in to Horizon Console by using a secure (TLS) connection. You can also use the IP address of the Connection Server instance instead of the FQDN, but this might result in blocked access or reduced security due to certificate mismatch. You cannot use https://localhost to connect from the Connection Server host, but you can use https://127.0.0.1 instead. The other options are not valid URLs for Horizon Console. References: Log In to Horizon Console