Hi witeku. For questions 1 and 2 I am not sure. But the rest I can answer.
1) I believe 10 tracks.
2) I believe right now it's 2 tracks, 1 platform, which is used for Beovoz/BG:Voz.
3) The status is that the works required for the full functioning of BG:Voz have been completed, and not much more than that. If you look back at some pages in this topic, you will see pictures of the latest progress.
4) Who knows? When the first Serb goes to space, or maybe later. For the Russian loan - no, it did not get it yet, and no, nobody really knows what is going on with that. Here we all wish we knew.
5) Also unknown. As far as I know, the "station building" is the thing you will see in the pictures in this topic, that is the platforms and tracks. The roof of the station building is a flat concrete block, on top of which, according to the latest plan, a shopping centre or something like this will be built.
6) The City financed the works relating to BG:Voz. The rest is up to Zeleznice Srbije, that is, the national government.
7) Zeleznice Srbije operates BG:Voz under what is apparently quite a strict contract with the City of Belgrade. This is unlike its predecessor, Beovoz, which was solely under the jurisdiction of ZS and therefore insanely unreliable.
8) No. It is planned in the first half of this year.
9) BG:Voz is not a metro system. BG:Voz is commuter rail, like S-Bahn or RER. When someone calls BG:Voz a "metro", it's to attempt to fool the public and obscure the fact that in Belgrade we have been talking about the metro since the 1960s without actually laying a single cm of track for it. BG:Voz, i.e. the railway junction, is planned to intersect with the metro (more or less in all the different plans presented over the years) in several places. One of them is Prokop, where as far as I know already a "cassette" than can be used for metro station construction has been built (when work on the station first started). Another planned intersection is Vukov spomenik station. Some metro plans also have the two systems intersecting at Novi Beograd railway station, and I think also at one station in Zemun.
10) Vukov spomenik is supposed to be both a metro station and a station of the railway junction. Only the station for the railway junction has been built. According to plans, the metro station should be built next to it with a corridor connecting the two.
Here you can find plans of proposed systems for the Belgrade metro. The big map is the project from 1976 which was adopted by the City and was supposed to be built. It has plans for both city metro ("metro") and commuter rail ("regionalni metro"). As you can see this plan envisions something like BG:Voz not using the railway junction, but being its own independent system.
In the 1980s this plan was abandoned by shortsighted politicians, who instead implemented the "Tram for the 21st century" project, extending the tram system throughout the city (the full plan was never implemented due to war in the 1990s) instead of building the metro. Also, the regional metro was axed and instead we got Beovoz, using the railway junction.
In early 2000s, a plan was adopted (that is still official on paper, but de facto has been also abandoned) for an LRT system called the "Belgrade Light Metro" (Belam). Here is a map:
http://www.beoland.com/LRT/pic/sema_metroa.jpg This is just basically a glorified tram system that has some stations undeground - it is not even fully grade-separated from traffic along the whole route. You can see both in the 1976 metro and Belam intersections in Prokop, Vukov spomenik, and Novi Beograd with the railway junction.