Make change in Hubspot UI



We are working on Hubspot Sales product. Now for one of the requirement we need to make change in Hubspot UI, we need to make validation on certain fields (i.e. Mobile No) field and make some of the fields mandatory during Contact and Deal creation.

Is this possible in Sales platform or it is only possible using Marketing platform. How do we leverage marketing platform to achieve the same?

Thanks for the response in advance.

Rahul Soni.