The chasis number on a car can be found most likely close to the engine, on the body frame. It depends on the make or brand.
Toyota
You can look at the engine to find the chasis number of a Toyota Corolla.
its chasis could be loose or its just old chasis being he thing that holds the wheels to the car.
catalytic convertor breaking down, or exhaust touching body or chasis of car
the chasis number is located on the back of the bolthead.
If your vehicle has grease joints, every oil change.
it is engraved below the drivers seat
A frame is the skeleton of a car without the mountings, were as a chasis is a mounted frame.
2 places, on the front door pillar and on the firewall.
You can find barcode label fixed in rear seat side glass. You can see big numbers in that bar code label or you can open hood and see below the wiper.
NO. A car mileage represent not only the engine, but the total depreciation of the car. like, gear, chasis, stearing system , electrical system etc....