Is this possible to have different versions of Erlang/OTP installed simultaneously on the same platform?
It is no only possible, but also very frequent. On my machine I have one version that I installed for development (R13B03) it is the default version when I launch erl. A second copy of the same version associated with nitrogen. this copy is used when I start my nitrogen website. The version will not change when I will use the R16B.. for development A partial older version which came with the installation of Wings3D.