If you look at the User Fields options, you will see...
*You can re-postion the fields by drag and drop above/below each other.
*You can not remove the system default fields, only re-position them.
*When choosing the dropdown/radio type field you need to add options seperated by comma.
*Show label is whether to show label above the field on singup/edit form or not.
*Non-required fields are not shows on signup form.
You are correct, the "Login in with Mobile Number" field is not listed, but you can sort the Birthdate, Gender and your custom fields in the order you want, with the mobile number field being before all of those.
Given that the mobile number field is not listed, I believe this would have to be re-coded by developers to show as a default with the Birthdate and gender fields as I believe these are part of core files.
You can achieve:-
- Birthdate -> Gender -> Occupation (custom) -> Status (custom)
With the mobile number being shown before all of those.