Let us say that you have a APS sensor 24Mp with the same S/N as a 24Mp 24x36 sensor then it is an optical question, it is hard to make a APS lens 1,5 1,6 times better which is require compared to 24x36mm lens.
This is incorrect.
Because there will be less absolute magnification for a same-sized print with the larger format, even if the sensors have the same pixel dimensions, the larger format will be sharper and have less noise. Again, always assuming all else is comparable, including a longer focal length lens for the larger format.
is it, if the S/N and Mp is the same from the two sensor areas, then it must be an optical question , and there the APS lenses must be 1,5 1.6 better than the 24x36mm lens.
As I already explained, it is a question of how much enlargement is necessary for a print.
If you're making a 24" x 36" print, the APS-C image will be enlarged 41x from the sensor's original size of 14.8mm x 22.2 mm, but the full-frame will only be enlarged 25x from the sensor's original size of 24mm x 36mm.
Whether you measure S/N in noise per pixel or noise per square mm of sensor, because you've got two and a half times as many square mm of sensor per pixel with the larger format, you're getting that much better of an overall signal to noise ratio.
Imagine you were back in the days of film. You have a 35mm camera loaded with Velveeta on one tripod and an 8x10 view camera loaded with the exact same film on a second tripod. The 35mm camera has a 50mm lens and the view camera has a 400mm lens, both of which give the same normal field of view on the respective cameras.
You'd agree that, since it's the exact same film, the exact same chemistry, that the S/N ratio is exactly the same, right?
Now, let's say we're making an 8" x 10" print from the exposure. The 35mm negative needs to get enlarged 7.5x to make the print, but, for the view camera, it's a contact print.
If you don't agree that the contact print from the view camera will be dramatically sharper and have far less grain than the enlargement from the 35mm camera, then you truly are hopeless.
Now, you might still argue that the pixel dimensions are relevant, but I'll show they're not.
Let's not use traditional printing methods, but rather scan the film. But we want to wind up with the same megapickle files for both, to simulate this contrived example. We're going to scan the 8x10 negate at a lowly 300 ppi, and we're going to scan the 35mm negative at a whopping 2250 ppi. We're still going to make an 8x10 print, and we're going to do it at 300 ppi. And, because of the resolutions I picked, it "just happens" that no interpolation of either file is necessary; both will still print at 300 ppi at 8" x 10".
Once again, if you still don't think that the print from the 300 ppi scan of the view camera's negative will blow away the 2250 ppi scan from the 35mm camera, you're hopeless.