Regarding your second question, I know the answer is yes. I have kept two versions of MATLAB on my machine simultaneously. During the installation process, just make sure that they install into different directories. (I think that will be the default behavior, because it uses the release name as part of the directory names.) Also, if you use a desktop icon to launch MATLAB, be cognizant of which version you are starting up, because I think that by default, the new desktop icon will overwrite the old one. (Not 100% sure on that.)
Regarding your first question, it sounds to me that you need to download the 32-bit version, but I cannot say that with complete certainty.