Can I be found liable if I part-exchange a car that I suspect has faults?

I'm part-exchanging my car for a new one (to a garage). He turned the car on and back off and said his checks were done, but I think there's an issue with the EGR. However, I'm not a mechanic. Do I need...

Am I liable for part exchanging a car that was previously modified before the sale?

I recently sold a car to a dealership and one of the questions was is the car modified and not standard. I said no as I was unaware it was modified and it is now been changed to the dealership on the V5....

What's the best time to part-exchange a car?

We want to get rid of our Skoda Karoq before the manufacturer's warranty runs out on 28 February next year. When do you think the best time would be to p/x between now and then?

Honda CR-V (2007 - 2012)

Roomy and versatile. Very comfortable, pleasant and relaxing to drive. not at all cumbersome. 2.2 i-CTDI diesel is excellent.