Let G be a compact subgroup of GLn(R) and 0 ≤ s < r < ∞. We prove that every definable C^SG map between affine definable C^rG manifolds is approximated in the definable C^s topology by definable C^rG maps. We show that each G invariant proper submersive surjective definable C^r function defined on an affine definable C^rG manifold is definably C^rG trivial. Moreover we prove that every noncompact affine definable C^rG manifold admits a unique affine definable CrG compactification up to definable CTG diffeomorphism when r ≥ 2.