mojoPortal is still compiled for 4.0 and I don't recommend you change that or modify any mojoPortal code. Actually, only the UI projects are even compiled for 4.0, the business and data layers are compiled for 3.5 because we use the same ones in our package for 3.5 and we don't need any new 4.x functionality in those projects. So we have 2 versions of each ui project so that we can still compile packages for 3.5.
So 4.5 is our recommended hosting environment now and mojoPortal runs great under that framework but we are not yet compiled for 4.5 and not able to use any new tidbits that are only in 4.5 yet, though you could in your own custom projects. ie you can change the build targets in your custom projects to 4.5 if you want but I don't suggest you modify anything in mojoPortal projects at all.
There are no needed changes in web.config and no app pool settings needed changing on my server as mentioned in my previous post. There is no new app pool for 4.5 in a production environment. On my win 8 dev machine I did change my dev site to use a 4.5 app pool since one exists but no such app pool exists on my server.
4.5 is completely compatible with 4.0, but new 4.5 features can only be used if you do compile to that framework.