How to Release Customization and Personalization Restrictions?

I am currently unable to access the personalization settings on my Windows 10 computer, as the options for changing themes, colors, desktop backgrounds, and lock screen images are all grayed out or disabled. I suspect these customization and personalization restrictions have been applied either through local group policy, a registry edit, or an organization's management policy, and I would appreciate step-by-step guidance on identifying the specific restriction and safely reversing it so I can regain full control over my system's appearance and user interface settings.

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