I'd like to know, if with the version >2.73 it's possible to have an URL for the admin interface ( used an intranet URL) and an another URL for the public survey (internet URL).
This is not a feature of any LS version afaik. You might be able to work around this with custom coding, redirecting, etc, but I don't know if and how this is possible.
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Provide your LS version and where it is installed (own server, uni/employer, SaaS hosting, etc.).
Always provide a LSS file (not LSQ or LSG).
Note: I answer at this forum in my spare time, I'm not a LimeSurvey GmbH employee.