Certifying reliable sources for quantum information processing is still one of the major challenges towards practical applications. Optical approaches to quantum information processing are being one of the most promising platform, thanks in particular to the ability to generate very efficiently large entangled states- cluster states. However, there are still many fundamental challenges, in particular on how to generate, measure and certify the class of states necessary for quantum advantage. We have developed a platform based on optical time-frequency modes, that we use to multiplex continuous variable quantum information. We use mode selective single photon operation in order to produce multimode non-gaussian states, the key ingredient of continuous variable approach to quantum processing. However, the complexity of these states does not allow for an efficient full tomography. Hence on the one hand we developed tools to characterized and certify specific quantum properties, such as Quantum Non-Gaussianity and Wigner negativity. On the other hand we propose a witness based on steering and Fisher information, to witness purely quantum non-gaussian correlations.