Hi

I recently bought a Mazda 2 Demio, 2014 model used. But my experience so far was not smooth at all. I suspect that the dealer has tampered with the car.
For some time a glow plug indicator was flashing, and there was a "Glow Plugs are preheating" error on the screen. So I took it to the dealer multiple times and he was insisting that there is nothing wrong with the car.
I was also having issues with the DPF. The car was regenerating every here and then but no DPF light was turning on.
Now after some time I discovered that the oil was being diluted with diesel as a consequence. So I took it to him and requested to fix all issues while I was missing abroad.
So I receive the car, and the glow plugs are no longer flashing. He said that he replaced them.

But one thing I ve noticed is that when I turn on the car, and all indicators are lid for a a second or two, the glow plug indicator is the only one that in turns on and off for a fractions of a second. You can barely catch a glimpse of it.

I am wondering if this is the normal duration of the glow plug indicator showing up when the car is turned on.

In addition now the DPF is flashing and the dealer said that he can remove the insides of the DPF barrel and install a program so that the car's computer ignores it.

But the worrying thing is that I have found out that some mechanics do not remove the DPF, they just tamper with the software so that the car bypasses DPF related readings while the problematic DPF is still there causing serious damage in the long run.

So now I am wondering:
a) if the Glow Plug reading/indicator has been tampered with and if there is a way to find out
b)How long do the Glow Plug indicator remain on when the car is turned on? If someone can post a short clip of their indicators that would be very helpful
c)if there is a way to reset the car back to how it was before it was tampered so that all error indicators will be read again
d) if there is a way to discover if the DPF was indeed properly removed