if you're approached by police my advice is to shoot them... with your camera, they might not like it and usually they don't but it's legal, if your rights are violated you'll be able to prove that
they have the right to check your ID if there's suspicion of crime, you have the right to know the reasons for ID examination
in case of detention they must explain the grounds for their actions
don't sign anything you can't understand (pretty much common sense but under pressure people sometimes concede)
Hanna, I don't doubt your experience and I believe it's rather norm than exception, it should be however noted that first of all you're a woman and women are much less prone to conflicts with laws everywhere, and secondly the general climate has changed since Yanukovich came to power (i don't know how long ago you visited), the police regained its confidence which is potentially hazardous when coupled with judiciary illiteracy, poor training and discipline, low cultural level and virtual impunity
Of course the climate first and foremost affects the local population however it might occasionally rub foreigners as well
The guy in the video was talking about stolen 40 Euros, he tried to say 500 but immediately corrected himself