1) Which side fired the missile?

According to the Dutch Prosecution Service it was fired by the Russian crew of a Buk Telar. I have seen no conclusive evidence for that. In a document of the Dutch military intelligence service (MIVD) it is stated that western intelligence services have spotted seven Ukrainian Buk Telars in Eastern Ukraine and no Russian Telars.

2) What are the characteristics of the identities and backgrounds of the four suspects?

The defendants are three Russians and one Ukrainian: Igor Girkin, Sergey Dubinsky, Leonid Kharchenko and Oleg Pulatov. They are accused of complicity in the shooting down of Flight MH17 and having killed all 298 passengers. Their specific involvement is said to have consisted of: demanding an anti-aircraft system with crew, specifying a suitable launch site for that system, as well as transporting and guarding it. The person who ordered the missile to be fired and the person who actually pushed the button are still at large. It is unclear who they are and why they launched the missile.

3) Will the verdict have an impact on the current situation in Russia and Ukraine?

I don't think so.

4) What unknown doubts still exist about the incident?

There are many. There is no conclusive evidence that MH17 was shot down by a Buk missile and that this missile fired by a Russian crew. The Prosecution has said that they think that the crew of the alleged Buk Telar mistook MH17 for a military plane, but the Prosecution did not substantiate this claim. I interviewed the former commander of a Buk unit. He said it is impossible for a highly trained crew of a Buk to mistake a passanger plane flighing at 10 kilometers heigth for a lowing flying fighter jet. In fact nobody knows why the missile was shot.

5) Are the current findings of international organizations credible? What is the difficulty of a cross-border investigation?

The criminal investigation was conducted by police officers and prosecutors of The Netherlands, Belgium, Australia, Malysia and Ukraine. Many think the investigation is corrupt because of the participation of Ukraine. The secret service of Ukraine has provided much of the evidence, among which phone intercepts. It is unkown if these are original audio files. 

6) What fake news is currently surrounding this incident?

The Ukrainian authorities have promoted several photos and videos of a Buk Telar in areas that were held by the pro-Russian seperatists. It is unkown if these photos are real and if they were taken at the day of the crash.