About Management Representative

Answer:

There is no requirement that states in ISO 13485 on the number of management representative for an organization.
A Management Representative should be someone who is knowledgeable, trained and have experience in dealing with the Quality Management System of the company as well as familiar with the Standard applied.

You can also refer to the below link on:
How to define roles and responsibilities within an ISO 13485-based QMS https://advisera.com/13485academy/blog/2017/11/16/how-to-define-roles-and-responsibilities-within-an-iso-13485-based-qms/

Is it mandatory to create a management review SOP if the quality manual mention about the management review process already?

The Standard requires a documented procedure for the Management Review. It will be recommended to supplement the Management Review procedure with a SOP if the procedure stated in the Quality Manual is brief.

For more information, please refer to :
How to Perform Management Review According to ISO 13485
https://advisera.com/13485academy/blog/2017/11/09/how-to-perform-management-review-according-to-iso-13485/
Procedure for Management Review
https://advisera.com/13485academy/documentation/procedure-for-management-review-iso-13485-2016/