I've installed the latest version (taken from Windows Store) and Skype does not work any more. Please tell me how can I install the previous version, or when do you plan to release an update to fix this issue?
You will have to contact the developers of the application. Only they can provide the necessary information about this request. Additionally, they might ask you to provide log files if you tried installing the application on Windows 8.1 and failed. Most likely, they'll release an update to fix the issues with the current version or release an entirely new version.
You can use the following URL to learn how to access Customer Service: https://support.skype.com/en/faq/FA1170/how-can-i-contact-skype-customer-service