Well... It has been quite a long time but the BEST solution was to sell Liana and buy another car. And that's exactly what I did in June or July 2011 after struggling with this problem.... :).
The person who purchased the car simply changed the engine and replaced it with Corolla engine with front suspension. And he was very happy after that.
So, the solution for overheating problem is;
Change Thermostat valve
Replace the engine or, at least, assembly. DO NOT go for engine overhauling as multiple times overheating would have destroyed the engine.
Simply Change the car
Well these suggestions re based on my experience and any one can disagree.
In 2011, new assembly for Liana was for Rs. 30,000 but my Liana was Peshawar number, I was not interested in changing assembly as for that I would have to get the engine number changed on the book.