Then, is there a way to know which HW does support texture lookup in the vertex shader? Runtime? Is there a list (e.g. at NVIDIA) for different models?
The GeForce 6 has limited support for vertex texture fetch, see NVIDIA’s Using Vertex Textures. I believe the GeForce 8 has full support for vertex textures, given its unified shader architecture. One exception is computing mipmap LODs, which is only available in fragment shaders.