when upgrade on 4.9.5 on host, we have at the bottom other modules that you can install and also the upgrade module present on your host.
i preconise to install the modules you want in 4.9.5 before to do the upgrade on 5.1.2.
I have also probleme with free skin not compatible with 5.1.2 iand i want to delete before upgrade on 5.1.2
catalook necessite upgrade to run on 5.1.2, i must upgrade to catalook v5.8.9, i suppose that is also why i have display problem with the site using this modules.
in the first time upgrade, i have installed 5.12 after 4.9.5 the upgrade is more long than 4.8.4 to 4.9.5 and also the modules peresent (on 4.9.5) at the bottom page when connecting on host=>modules are not present.
probleme to display the US language does not existe, only the language selected on host default language before upgrade is present ( i dont know if other are present if you have more than 2 languages)
it is possible that i upgrade on 5.1.2 but before i would like to know if it is a good idea or does i must wait the 5.2 ??
regards