Integrating LS Retail 2.0 POS with a 3rd Party REST API

I have a few questions to ask since I am pretty novice to Microsoft Dynamics -

  1. A client of mine is using LS Retail 2.0 POS with Windows Xp. What version of Navision is he using in that case?

  2. What is the best way to call a PHP based REST API GET / PUT / POST / DELETE (3rd Party) through it?

  3. How can I make compatible Dlls / OCXs that can be used to call this REST API. Will I need to get down to native C++ as the version of Navision is pretty old?

Any help related to this would be highly appreciated.