Let me try and cover everything that's been raised:
Beta releases: I tested this with the live version and could definitely choose a beta release and Steam downloaded and installed r117 correctly. (I did notice the dropdown box for beta releases seemed kind of "sticky", but closing and reopening the properties dialog seemed to fix it.) However if you have both the Free edition and the Personal edition installed, they should be sharing the same files, so you might need to set both to use Beta releases. If you have any other issues with beta releases I'd advise you contact Valve, since as far as I can tell everything is set up correctly on my end.
Portable version: if you install Steam on another computer and log in, it should allow you to use Construct 2 on there as well. Beyond that it's out of our control I'm afraid, you'd need to ask Valve for changes to that process.
Standalone license in addition to Steam copy: I'm not sure we can do this, since sending a standalone license amounts to a second independent copy of Construct 2, which would normally cost double. Since we aim to have simultaneous beta and stable releases on Steam (and x64 support soon), I don't see any disadvantage to buying the Steam version - you can still create desktop shortcuts and the like, you just need Steam running at the same time as C2 for license authentication. This is totally normal and how everything else on Steam works.
@andreyin - you definitely can't install the version from our site over the Steam files. They are different builds (the license systems are different, as well as other changes). If there's an error you'll get the free edition, so you won't be able to use a license if you copy files over Steam.