1. There has been a Joomla extension called "joosurvey" but this is completely outdated and not maintained anymore.
You can run Limesurvey within an iFrame of a joomla system I guess but you might need to code some scripts to use the same user information. More information:
1.1 Search the forum for "joomla".
1.2 Maybe you can use the one-time-password feature to login joomla users to the admin backend:
docs.limesurvey.org/tiki-index.php?page=...e_one_time_passwords
1.3 Check the CMS integration settings:
"// CMS Integration Settings
// Set $embedded to true and specify the header and footer functions - for example if the survey is to be displayed embedded in a CMS
$embedded = false;
$embedded_inc = ''; // path to a php file to include
$embedded_headerfunc = ''; // e.g. COM_siteHeader for geeklog
$embedded_footerfunc = ''; // e.g. COM_siteFooter for geeklog"
2. You can forward the user to a script which has to be coded and calcultes the score at the end of the survey and redirect them automatically to another survey.
3. You can run X surveys with Y users at the same time.
a-e) This can partly be done with some additional coding.