Question about Venus Optic Laowa 25mm f/2.8 2.5-5x UltraMacro Nikon AI

Yes, and with full-frame sensors too.

Yes.

The lens is suitable for FX (full format) so that DX (smaller image circle) is covered without any problems. With DX you only "give away" a little image circle and get an approx. 1.5-fold "enlargement" so that it no longer corresponds to a focal length of 25mm, but you effectively take photos like with a 37mm FX lens.

PS: The lens is super-sharp in resolution; amazing!