1) What is the maximum file size for zip and rar files when posting new uploads to this site?
8 MB, at the moment.
2) Can we use off-site links to MediaFire, if for example a Residential/Community Lot exceeds the file size limit for uploading them here?
If your lot manages to be bigger than 8 MB, SOMETHING IS WRONG WITH IT, and we suggest you not upload it at all because it will probably corrupt someone's game if installed.