jaikumar1 : To enable responsive on your community, you must raise a support ticket with Lithium.Lithium will then turn on responsive and make the necessary changes to the quilts/layouts/components. You can then start working on that environment.Check this Documents which will provide more details about Responsive.
https://community.lithium.com/t5/Responsive-for-Developers/About-Lithium-Responsive/ta-p/218740
https://community.lithium.com/t5/Responsive-for-Developers/About-the-Responsive-message-view/ta-p/254356
https://community.lithium.com/t5/Responsive-for-Developers/Feature-versions-Responsive-Base-Responsive-Peak/ta-p/285134
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Thanks & Regards,
Abhishek Illindra