I think when Rajveer spoke about "Darwaaza" he meant that up unitll now in his life he had never thought about love or falling in love. He did not ever give importance to loving someone or anyone for that matter. He now feels that he wished he had looked at girls and had fallen for someone then this situation of a mock engagement with Ritu or being rejected in love by Naina would never have arised. I think this is what he meant. He does not love Ritu at all. He was merely referring to the present situation and not Ritu or propsing to Ritu.
No offence intended to Ritu fans.