theme my login custom fields

Im am making a website which requires a user to enter a variety of details on registration. I have been able to add a few custom fields to the register-form.php.
I have three questions:
1 – how do i make fields mandatory and others non mandatory?
2 – Once the user has entered their details how can they edit them, in the dashboard only the generic fields are their but non of the custom fields that i have added into the php file.
3 – is there a short code for a edit details page similar to the pages that are setup for login, logout, register and forgot password?

Thanks