Your survey site is where you build surveys and collect responses, at an address like yourname.limesurvey.net. It comes with your LimeSurvey account: you sign up once, and LimeSurvey creates the site when you log in for the first time.
Open the address of your survey site and log in with your username and password. The username is case sensitive.
Note: When you sign up, your survey site uses the same username and password as your LimeSurvey account. The two passwords are separate afterwards: the admin password of the survey site is reset on your account page. See Can't log in? Reset your password or recover your account.
The Your survey site block on your account page at account.limesurvey.org holds the address, the domain alias, the storage and response reminders, the location, your used and remaining responses, the admin password and Delete survey site. See Manage your account and survey site.
On your account page, under Your survey site, next to Survey site URL. View survey site opens it.
Yes. See How do I change my survey site domain?
Yes, with their own users on your survey site. See Manage administrators.