Looking to lock form on email submission and set something from the form in the email subject

[lostfrogg]

I have added an email submission button. I've looked around but can't seem to find the answer to this - how do I lock the form on submission? The form has an auto-populate today's date box, and currently every time I open the form it resets it to the current date. 

Second, I have fields on the form for "forename" and "surname". Would it be possible to have the following in the "email subject": 

[specific text] - (forename initial) (surname initial)

Thanks!