Need Complete eCommerce Solution (Inventory Mgmt, POS, Online Checkout, etc)

Must have support for Web, iOS and Android platforms Must be based on .NET/SQL Platform Must transfer all copyrights and complete ownership of the code. No third party subscription We are NOT a retail shop but a software development company by ourselves. We can develop it all by ourselves but it will take time that's why we want to buy something that's already proven working. Must be able to provide access to demo environment for us to explore all the features offered. Not interested in outsourcing our work or monthly support. Only interested in flat out purchase. You will be required to install application on to our test servers and make it work before we accept your work. There will be no milestones.