The source control operation used to store local changes on an instance for later application is called a stash.
A stash is a temporary storage area for uncommitted changes that are not ready to be pushed to a remote repository. Developers can use stashes to save their work in progress without committing it to the local repository or discarding it. Stashes can be applied later to restore the changes to the working directory, or dropped if they are no longer needed. References: [ServiceNow Docs - Stash local changes], [ServiceNow Docs - Source control] Reference: https://docs.servicenow.com/bundle/orlando-application-development/page/build/applications
/task/ t_StashLocalChanges.html

Catalog Client Scripts and Catalog UI Policies are the client-side scripts that apply to Record Producers.
Catalog Client Scripts allow you to add or modify functionality on a catalog item or record producer form.
Catalog UI Policies dynamically change information on a catalog item or record producer form. UI Scripts, UI Actions, Client Scripts, and UI Policies do not apply to Record Producers. Reference: Catalog client scripts, Catalog UI policies Reference: https://docs.servicenow.com/bundle/orlando-application-development/page/script/client-scripts/ concept/c_CatalogClientScriptCreation.html

https://developer.servicenow.com/dev.do#!/reference/api/rome/client
The GlideUser object (g_user) is part of the client-side scripting API that provides information about the current user and the user's preferences. It can be used in Client Scripts and UI Policies to customize the user interface based on the user's role, language, time zone, etc. The workflow.scratchpad object is only available in Workflow scripts, which are used to automate processes on the platform. The current and previous objects are only available in server-side scripts, such as Business Rules and Script Includes. The GlideSystem object (gs) is also a server-side object that provides methods for logging, debugging, date and time calculations, etc.
References:
[GlideUser object (g_user)]
[Workflow scripts]
[Business Rules]
Script Includes
[GlideSystem object (gs)]

You must script and configure all required behaviors Provided link has this statement: Extending an existing ServiceNow table means the new table inherits the parent table's columns as well as its business logic.
The following statements apply when extending an existing table:
The parent table's Access Controls are evaluated when determining access to the new table's records and fields. This is true because Access Control (ACL) rules are inherited from the parent table to the child table, unless the child table has its own ACL rules that override the parent table's rules. ACL rules are used to restrict the access to the data and functionality of the ServiceNow platform based on the user's roles and conditions.
The new table inherits the functionality built into the parent table. This is true because the new table inherits the business logic and the relationships from the parent table, such as Business Rules, Script Includes, UI Actions, UI Policies, and Reference Fields. Business logic and relationships are used to define the behavior and the structure of the data on the ServiceNow platform.
The new table inherits all of the fields from the parent table. This is true because the new table inherits the columns and the attributes from the parent table, such as Field Name, Data Type, Default Value, and Mandatory. Columns and attributes are used to define the properties and the characteristics of the data on the ServiceNow platform.
The following statement does not apply when extending an existing table:
You must script and configure all required behaviors. This is false because you do not have to script and configure all required behaviors when extending an existing table, as some of the behaviors are already inherited from the parent table, as explained above. However, you can script and configure additional or customized behaviors for the new table, such as adding new fields, creating new Business Rules, or modifying existing UI Actions. References: Table Extension, Access Control Rules