1) I wouldn't worry if everything appears to work, that warning is due to possible changes within MySQL's structure, as long as the two versions are fairly close you shouldn't run into issues.

2) Those errors are normal and nothing to worry about, it's features that are being added in but haven't been full implemented yet for the most part

3) With Skyfire i'm really not sure, Trinity tells you as soon as you start the Worldserver what version it is using