Redmine

I guess I am the new nightmare for this community: :-)

I am hardly trying to update a very old (v0.8.4) redmine server with 5 projects to a recent version.
I have followed the steps for 1.x and 2.x as written in http://www.redmine.org/projects/redmine/wiki/RedmineUpgrade I also read the forums and several other forums concerning the different error messages.

However, it keeps failing with several different error messages and I am completely stuck. Before I start to ask for all the errors in detail I wonder if somebody has a nice and clean way based on pure SQL (probably) and/or a good hint for a resource covering all versions in one.

And I also have a basic question: I wonder if I should go step-by-step through all the version / branches and/or try the big-shot with the most recent version?

Any hints are greatly appreciated.