Just simple question for the last 1.7.3 (or earlier) version.
Thanks in advance for response.

PS.Also, if is not possible one support member to be included in two or more response groups - please, take this note as request

Yes, this is the point - you can assign just one group to representative.
Also, you cant assign user to group.
How to accomplish this goal? If there is no such feature, must be include.
And answer (one possible)  to you - yes, I want this organization of users to be able to make slice of work: which group, how many tickets, which user, how many work and so on.

May be I don't over look something in the interface ?
Simple example: User Topper must be responsible for Internet, Software, ERP and CRM groups. Another user John must be responsible for Hardware, LAN, Internet, HelpDesk and UserSupport.
How to realize this if in user profile there is ONLY one group chosen with drop down menu ?

Hm, you obviously dont catch me - my quest was for Topper to be in ISEC and HLIHU. And more, not only two groups, group for every one purpose with separate email - Internet (inetrnet@domain.com) rep. Topper and John, Software (software@domain.com) rep. Topper, ERP (erp@domain.com) rep. John, Hardware (hardware@domain.com) rep. Topper and John.
This  is the way we use eTicket, but with notification email to the admin of desk, after that redirect ticket to specific representative and so on...
THAT was may question/request

I agree, that's the easiest way with the current version.  If you'd like to see it in a future version, submit a feature request in the feature request board.