Disclaimer: I am an MSYS2 developer
While MSYS isn't dead, I would say it's not looking very healthy either. It is a project started by the MinGW team many years ago as a fork of Cygwin that never kept up with Cygwin.
msysgit is a fork of a slightly older version of MSYS with some custom patches, old versions of Bash and Perl and a native port of Git.
MSYS2 is a project started by Alexey Pavlov of the mingw-builds team (who are the official packagers for MinGW-w64 toolchains) as a recent fork of Cygwin which tracks the latest Cygwin closely so that it doesn't end up out of date. Alexey forward ported the old MSYS patches and added some of his own.
As well as providing the necessary Unix tools with which to compile native software - the stated goal of MSYS - we ported the Pacman package manager from Arch Linux. Pacman is more than just about managing binary packages (though it does that very well). It has a software building infrastructure called makepkg that allows the creation of recipes (PKGBUILD and patch files) for building software.
IMHO, the adoption of Pacman changes things significantly for open source development on Windows. Instead of everyone hacking on their own bespoke shell scripts to build software in a hodge-podge, incompatible way, packages can now depend on other packages and PKGBUILD files and associated patches can be used as a reference for constructing new PKGBUILDs. It's as close to a Linux system as a (native) Windows can get (Arch Linux in particular) and allows for simple updating of all the installed packages.
We target Windows XP SP3 as a minimum and support both 32-bit and 64-bit Windows. We would ask that you never mix MSYS2 with msys or msysgit. Pacman is used to manage the whole system and as such, files from the other systems will cause conflicts.
We also try to upstream our patches to the projects we build and actively solicit contributions from other open source projects. We hope others find it easy to work with us.
Our main website is on SourceForge, and it contains links to our PKGBUILD repositories. We also have a more user friendly installer site on GitHub.
Feel free to join us on IRC (oftc #msys2) if you want more information.
No, MSYS2 does not directly support installing old versions of packages. Here are some things you can do though:
GCC is one of the harder packages to build and work with so it might be difficult for you to compile it from source. Also beware that the C++ ABI changed between GCC 4 and 5 or something like that, so binaries you build with the old GCC might not work with any of the MSYS2 C++ shared libraries compiled with GCC 5.
Best Answer
That typically is done by (e.g)
and then picking the package that you want from that result and doing (again e.g.)
Note that you need to use the correct bitness (i686 = 32 bit in this example).