Hi Alexander, for question one Immunet uses two cloud based detection engines which are ETHOS & SPERO. There is also the ClamAV engine which acts like a traditional AV. It downloads definition signatures to your hard drive which makes off-line scanning possible.
For question two, AV companys have to pay to have their products included on the sites you mentioned. The Immunet team has decided that this money could be better spent on other things like further R&D.
For question three, language translations have not been a priority for some time now. For this reason it's always best if you install the English language version to get the newest build of Immunet Protect.
For question four, Immunet uses a bootstrapper installer so an internet connection is required. Off-line installers are not generally offered because of the fact that it's possible for a hacker or other bad guy to compromise the installer with spyware or malware.
Best wishes, Ritchie...