glsl es 2.0 inverse matrix

No, there's no matrix inverse function in GLSL ES 1.00 (used in OpenGL ES 2.0). You'll need to do it manually, take a look e.g. here. But you should think hard whether you really need to do it in the shader on a per-vertex or per-fragment basis every frame, or is it possible to be precomputed and passed in as uniform.