No, you can't sign up like that - you can choose to register the firstname.lastname@gmail.com and it will make that your primary. If you sign up without the dot

No, you can't sign up like that - you can choose to register the firstname.lastname@gmail.com and it will make that your primary. If you sign up without the dots, you get an error message: "Someone already has that username. Note that we ignore full stops and capitalisation in usernames. Try another?"