Want to buy ShipConstructor2004

"Is it possible to work on 5 licences (up to 500 elements) on 5 workstation to get whole ship construction about 2500 elements - one ship unit will be done on one workstation ?"

Yes

"Is it possible to get CG of whole construction in Shipconstructor ? (in demo tutorial I can read only about CG of hull surface)."

Yes and No, if you are working the way you mentioned above, only the cg's of each "block" will be read but not the whole vessel.

"Is it possible to work in structure module without ShipCam - how to get/import cross frames etc. from hull model ?"

scin lisp, you call your sections and cuts from the boat i.e.. frames, longitudinal etc., using this lisp, (you must have already your frames and cuts done from shipcam), or you can use other software to create this sections and import them into SC2002 or 4

Maybe somebody who works in SC2002 and SC2004 will tell why I should buy 2004 (now we plan to buy 2002 because whole office is working on WIN NT 4.0 which doesn't support SC2004).

I don't know if you can actually buy SC2002 anymore, but my guess here is if you are going to do that and buy all this equipment, try to get the new versions, why should I do such expense and buy and old model?, remember that most of the designers and contractors out there will be upgrading in their first chance so, I will say, buy new, I'm guessing that your investment is because you have some work to be done, it will strangle profits but it will leave the office bright and shine with new equipment.

Besides AutoCAD changed the format of the dwg, so you will find yourself in the position of not be able to read files from a client or designer and ask them to send it in 2002 format, it sounds not like a big deal but when you have to exchange very important information and somebody forget to save it as a 2002 then becomes an issue.

and again, IMO I won't be "trying" to get the latest version, I will get the new versions and upgrades if I was in the position of doing that.