Infopath 2013 - hide fields when 'New' form is filled out, show fields when form is 'Edited'?

I have been asked to hide some fields on an InfoPath form when a user selects 'New Item' or 'New Form', but then un hide the fields when the form is opened in 'edit' mode - is this possible and how would I go about doing this? Also, with the above form, I have been asked to make one field mandatory when a user selects 'New Item' or 'New Form' so that the field is filled in, but when the form is opened in 'edit' mode, the field must not be mandatory - is this possible and how would I go about doing this?

Thank you very much for your time and assistance -

Kind regards,

Janice