Create a Firefox browser extension -- 2

Main object of the extension To redirect the user to another url if the main entered by the user is blocked by the isp. The list of main url and alternative url will be loaded from our database via external json. The requirements are as follows: - The extension will detect the page that has been blocked by the isp (detect by page connection reset or page no content loaded) and redirect the user to the alternative url. If the alternative url is blocked then will redirect to the next alternative url. - The extension will be installed to Firefox Portable Version (Windows, Mac). Please make sure the extension it works for both version. - Able to auto update the list of main url and alternative url whenever the browser is started. The list of main url and alternative url will be loaded from a external JSON url. (sample json format attached). The JSON url is hardcoded inside the extension. - The extension must able to prompt user if there's any new update to the extension. (Please advice on how to do this) Freelancer with experience in creating firefox extension will be preferred. Links [login to view URL] (firefox portable windows version) [login to view URL] (firefox portable mac version)