Sony India - Bad product, bad service

I bought a SONY DVD Hi-FI Audio System MHC-GNZ88D s/n 6108464 from Sony World, Noida, U.P, India on 12-04-07. Within a couple of months, it stopped playing DVD's. The system was under warranty and I gave this set for repairs at NRI Electronics Noida, which is a Sony authorized service centre. I was communicated that the motherboard had problems and will be replaced. It took them one and half months to replace the motherboard and another 2 weeks to make it region free.

Once it was back from the service center, it started playing DVD's but the response was very sluggish, it took lot of time to load the DVD's and started skipping tracks.

After that, I did not use this system for six months as I was out of town.

Once I was back and started the system, the DVD became unresponsive.

I called customer care and they told me to give the system to NRI electronics, so that NRI can send the set to Mathura Road, which is the Head Office in North India.

I gave the system to NRI electronics on 04-Oct-08 with clear instructions that this system has to be sent to the head office and not repaired. The customer care exec also called NRI with the same instructions.

On 05-Oct-08, I got a call from NRI electronics that the system is fixed.

They informed me that the Optical Lens was weak but in working condition, and I can take the delivery of the system.

My issues are as follows:

1. Why did NRI electronics repair the system, when they had to deliver this to the head office? (Maybe they replaced the lens in the last service and are now scared that the main service station will detect this).

2. How can the optical lens go weak without any usage?

3. What are the chances that other parts in the system have not been replaced by NRI electronics? Does Sony India conduct audits?