Comprehensive and Detailed Step-by-Step
Understanding Scoped Applications:
Scoped applications in ServiceNow are designed to isolate and protect application-specific code and data. Server-side scripts within scoped applications can use the gs (GlideSystem) object for logging and debugging purposes. However, not all gs methods are appropriate or valid for scoped applications.
Valid Logging Methods in Scoped Applications:
gs.info():
This method logs informational messages to the system log. It is commonly used for general-purpose logging when developers need to track execution flow or display debug data. Example:
gs.info('This is an informational log message.');
gs.error():
This method logs error messages to the system log. It is used to indicate problems or issues encountered during script execution. Example:
gs.error('An error occurred during script execution.');
Incorrect Options Explained:
gs.debug() (Option B): This method is not valid in scoped applications. It is a legacy logging method available in the global scope but restricted in scoped applications.
gs.iog() (Option C): This is a typographical error and not a valid gs method in ServiceNow.
gs.logError() (Option E): This is not a recognized ServiceNow API method. To log errors, gs.error() is used instead.
Best Practices for Logging:
Logging should be meaningful and avoid unnecessary entries to keep logs clean and manageable.
Avoid excessive use of logging in production environments, as it can clutter the system logs and potentially degrade performance.
Reference:
ServiceNow Developer Documentation on GlideSystem (gs).
SN Pro Tips on debugging and logging practices in scoped applications.

The Field Watcher is a debugging tool that allows you to monitor the values of fields on a form as they change due to scripts or other actions. It can be used to debug Business Rules, Client Scripts, and Access Controls, but not Script Includes. Script Includes are server-side scripts that define reusable functions and classes. They are not associated with any specific field or form, and therefore cannot be watched by the Field Watcher.
References:
Field Watcher
Script Includes

This class allows you to create and manipulate dialog windows on the user interface. You can use this class to display messages, forms, or custom HTML content in a modal window.
GuideAjex: This class allows you to make asynchronous calls to the server and process the response. You can use this class to retrieve data, execute scripts, or perform actions on the server without reloading the page.
GuideForm: This class allows you to access and manipulate the fields and values on a form. You can use this class to get or set field values, show or hide fields, add or remove options, or validate field inputs.
The class GuideRecord is not part of the Client side scoped APIs. GuideRecord is part of the Server side scoped APIs, which are a set of classes and methods that allow you to interact with the database and perform server-side logic on the ServiceNow platform. GuideRecord is a class that represents a record in a table and allows you to query, insert, update, or delete records on the server.
References:
[Client side scoped APIs]
[Server side scoped APIs]

https://www.servicenow.com/community/it-service-management-forum/email-notification/m-p/695221 Reference: https://community.servicenow.com/community?id=community_question&sys_id=e017cbe5db1cdbc01dcaf3231f9619a3 When configuring the content of an Email Notification, the following syntax should be used to reference the properties of an event triggering the Notification:
event.<propertyname>.
ThisisthecorrectsyntaxtoaccessthepropertiesoftheeventrecordthattriggeredtheEmailNotification,suchasevent.
name,event.parm1,orevent.parm2.Forexample,{event.parm1} will display the value of the first parameter of the event.
The following syntaxes are not correct for referencing the properties of an event triggering the Notification:
current.<propertyname>.Thisisthesyntaxtoaccessthepropertiesofthecurrentrecordthatisassociatedwiththeevent, suchascurrent.number,current.shortdescription,orcurrent.state.Forexample,{current.short_description} will display the short description of the current record.
${property name>.getDisplayValue()}. This is the syntax to access the display value of a property of the current record, such as current.state.getDisplayValue(), current.assigned_to.getDisplayValue(), or current.
category.getDisplayValue(). For example, current.state.getDisplayValue() will display the state of the current record in a human-readable format, such as New, In Progress, or Closed.
${gs.<property name>}. This is the syntax to access the properties of the GlideSystem (gs) object, which provides methods for performing system operations, such as gs.now(), gs.getUserID(), or gs.getProperty().
For example, gs.now() will display the current date and time of the system. References: Email Notifications, Email Notification Variables