Mandatory fields in Contact Person: Customer Master

I would like to make fields like Gender, Function, Business Address fields as mandatory. Is this possible in SPRO? Please advice.

You can make these fields mandatory with the Account group transaction.
Path:
IMG-Financial Accounting-Accounts receivable and Payable-Customer Accounts-Master Data-Prepration for creating master data-define Account group with screen layout.
Here select, the group as '0001--sold-to party.
Next chosse either General data/Company data/sales data, where you need to make the changes.
Example: say for address, choose general data dobule click on that, next double click on address, finally select the fields you want to make mandatory, display only, hidden, etc.

The T.Code for that is OBD2.
This is the place where we can make the fields required for us to be madatory , optional, suppress.

These are called as linking rules.