The correct option is "1. Workflow." Workflows in JIRA define the series of statuses and transitions that an issue goes through during its lifecycle. By configuring a workflow with review steps, you can automate the process of ensuring that all new feature requests pass through a review before implementation. This helps maintain quality and consistency in the development process.

System maintenance in JIRA involves various tasks aimed at optimizing performance and ensuring stability. Regular monitoring of system performance metrics helps identify potential bottlenecks or issues affecting performance. Optimizing database configurations, such as indexing and tuning, can improve overall system performance. Regularly applying updates and patches provided by Atlassian also helps in addressing security vulnerabilities and improving system stability.

The JIRA User Server, often integrated with LDAP (Lightweight Directory Access Protocol) or Active Directory, is responsible for managing user authentication in JIRA. It authenticates users and authorizes their access to JIRA based on their credentials stored in the directory service.

When setting up automation, you can use Test Runner to test and simulate rule executions. Test Runner enables users to run their automation rules against sample issues or real data to ensure they function as intended.

Bulk Move in JIRA changes the projects of multiple issues, allowing them to be moved between projects. On the other hand, Bulk Edit modifies the field values of multiple issues without changing their projects. Understanding this distinction is crucial for managing issues effectively in JIRA.

By configuring workflows in JIRA, project administrators can define the transitions between different statuses of an issue. They can control which users or groups have permission to execute these transitions, thereby managing who can move issues through the workflow stages.

When designing a workflow for compliance or regulatory requirements, it's essential to consider incorporating necessary approvals, reviews, and documentation steps. This ensures that all necessary checks and balances are in place to comply with regulatory standards and mitigate risks associated with non-compliance.

When a plugin causes instability, investigating the plugin component is paramount. This involves identifying the problematic plugin, checking compatibility with the JIRA version, and troubleshooting any conflicts or errors. Managing plugins effectively ensures the stability and smooth operation of the JIRA application.

Customer Portal Permissions control what customers can see and do in the customer portal, including their ability to view existing issues. By configuring these permissions, you can restrict customers from viewing all the details of existing issues while still allowing them to create new ones.

Issues from one JIRA project can indeed be linked to issues in another project using the issue linking functionality. This feature enables users to establish relationships between related issues across different projects, facilitating cross-project collaboration and tracking dependencies.

JIRA Automation can be configured to send automated email notifications based on specified triggers, such as newly created issues assigned to a particular user. This feature fulfills the requirement efficiently.

JQL (JIRA Query Language) is specifically designed for querying and filtering issues within JIRA, aiding reporting.