Ahh yes there is my site in the list.
Downloading the EPiServer CMS 5 R2 SP1 gives me an file that is called EPiServer CMS 5.2.375.133.zip
I always saves a copy of the dll files for all versions of EPiServer. My latest files before R2 SP1 was was 5.2.375.7
After installing the Deployment Center I can´t do an upgrade to thing higher then before. (5.2.375.7)What is the version number of R2 SP1? And how do I see it in the Deployment Center?
And what is EPiServer 188.8.131.52 Tech Preview that I can see in the Episerver Manager?
5.2.375.7 = R2 (includes upgrade from R1)
5.2.375.133 = R2 SP1 (includes upgrade from R2)
You would have to upgrade to R2 first, then use the R2SP1 upgrade for the final stretch.
The tech preview is probably something released to evaluate R2 before it was released. Upgrading from that probably requires some manual hunting.