>1. States are three things. They have monopolized use of force, a group of people who execute this force, and a geographical area in which to execute this in.
Yes, so long as one does not omit the crucial point of the class nature of the state which underpins its very purpose in existing and using force.
>2. States, because of this group of priveleged people, will always create a ruler-class above them, preventing them from establishing a classless society because of Nomenklatura and such.
The differentiation of tribal communities into classes and the eventual emergence of the state were the results of primitive communal life impeding the material development of society. The state is an inevitable part of the development of human society in the period of classes. It will wither away once the final system of class exploitation (capitalism) has been defeated and the high material and cultural level associated with "from each according to his ability, to each according to his needs" becomes a reality.
>3. States aren't necessary to achieve socialism because of the previous point and because of Catalonia and the Free Territory achieving "Socialism."
There's already a thread discussing the Makhnovites, but as far as Catalonia is concerned see PDF pages 314-323 of the following for examples of the "socialism" of anarchist control of Catalonia: https://espressostalinist.files.wordpress.com/2010/12/espana.pdf
Also the words of Juan Andrade, one of the POUM's leaders and obviously not someone partial to the "Stalinist" view of events: "The anarcho- syndicalist workers had made themselves the owners of everything they collectivized; the collectives were treated as private, not social, property. Socialization, as practised by CNT unions, was no more than trade union capitalism. 'Although it wasn't immediately apparent, the economy as run by the CNT was disaster. Had it gone on like that, there would have been enormous problems later, with great disparities of wages and new social classes being formed. We also wanted to collectivize, but quite differently, so that the country's resources were administered socially, not as individual property. The sort of mentality which believes that the revolution is for the immediate benefit of a particular sector of the working class, and not for the proletariat as a whole, always surfaces in a revolution, as I realized in the first days of the war in Madrid.'"
The other two questions presumably don't require answers. On Kronstadt see (a Trot source): http://www.marxist.com/kronstadt-trotsky-was-right.htm