1. Incorrect.

a) Not everyone - a lot of people oppose Putin. https://echo.msk.ru, https://novayagazeta.ru Most content on these sites devoted to critisizing Putin and current regime. These people do this for years.

b) Not everyone from your list opposed Putin, for instnace Khlebnikov mostly concentrated on Beresovsky.

2. Correct. We don't have any official evidence. This means that the only thing we can do is to analyze what is available. The links you provided don't help much in this endevour.