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I've found on several sources that people claim that there is Scrum 2.0 or even 3.0 like in here http://www.scrumcrazy.com/file/view/Scrum30_HiddenSecrets_AgileDenverMarch2014.pdf/499980506/Scrum30_HiddenSecrets_AgileDenverMarch2014.pdf
Although it's not officially confirmed anywhere.
Is there any Scrum 2.0 or 3.0? If so where can I find well defined and reliable guide for it?
There have been five revisions to the Scrum guide. The linked PDF is talking about the lessons learned, which eventually triggered these revisions. It is common that not all Scrum enthusiasts are aware that changes have been made, I meet them often, but it is just called Scrum and no need for 2.0 or 3.0.
With the first publication of the Scrum Guide in 2010, and its incremental updates in 2011, 2013, 2016, 2017 and 2020, Jeff and Ken established the globally recognized body of knowledge of Scrum.
The latest version of the Official Scrum guide can always be found at http://www.scrumguides.org/ .
Revisions:
The official revisions page shows the changes overtime, here are other sources that describe the changes in more details:
