If give to PJ 1600X1200 in 4:3 ( G70 ) what i get in 2,35:1?

1600x1200

you just squeeze it vertically

You get 1600X (1200/2.35)

You get 1600X (1200/2.35)

That's not correct.

The signal does not change.

I depends on what he was asking, If he wants to know the active video area than it is correct. However you are right that the total area will remain the same.

Then why they dont give to the scaler this resolution? (G70 1600X1200) almost full HD!!! but 1440X920?

You send the projector 1600x1200 from the source, with 2.35:1 displayed in "stretch" mode. At 4:3, the people in your movies for example will look tall and thin. Then you use the projector's raster size controls to squeeze the image down to 2.35:1. I believe the correct term is anamorphic widescreen.