Create a cross platform virtual classroom software

Hello, our company is looking for a freelancer, which could develop software for virtual classroom (backend + fronted), which would connect to future LMS API. This software includes conferencing, video sharing, application sharing and similar features. Features are specified in document bellow. This application should be modern looking, easy to re-brand (default same as desing of LMS) primary focused on PC. There could be some possibility of using this software on mobile devices (iOS, Android). Result would be application with documented code and documentation about connection to API and requirements for API. Please post (when bidding) technology, which you use and feel free to ask us about details you need from us.