Is addressing risks and opportunities one time activity?

Is to be done periodically or to be done if there is any change in QMS process?

Answer:

Addressing risks and opportunities shouldn't be one time process. The risks and opportunities should be assessed any time there are some changes in the context of the organization and changes in the QMS. Additionally, during the management review, you need to evaluate effectiveness of the actions taken to address risks and opportunities and as an output of the management review, you need to define opportunities for improvement.

For more information, see: How to address risks and opportunities in ISO 9001 https://advisera.com/9001academy/blog/2016/06/21/how-to-address-risks-and-opportunities-in-iso-9001/