1. Does the system preserve formatting of my spreadsheet data such as bold or color font or indentation.
No. The system reads the pure data and ignores the formatting. Hence when you reexport the data it will appear without the formatting.

2. When I try to download spreadsheet with testcases etc. I get following error: "The file you are trying to open, "FeaturesTestCases_NuevoMail.xls", is in a different format than specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file. Do you want to open the file now?".
Check your security settings. The downloaded file is probably of zero bytes because of security settings. Please send mail to info@nuevosoft.com with the browser settings.