Einstein made contributions to the first quantum revolution (photons, 1905) and the second quantum revolution (entanglement, 1935). There is still basic mystery in the quantum mechanics (Feynman). The second quantum revolution is under development. The purpose of this book is to experimentally: (A) study EPR paradox and the nature of entangled particles/photons. (B) explore the mystery of quantum physics. (A) Thought experiment proposed in EPR paradox related with kinematic/dynamic variables (position and momentum) of entangled particles, while Bell inequality measure the intrinsic property (spin). We propose that in order to completely test EPR paradox, one should also test the intrinsic nature (particle and wave nature) of entangled particles.(B) Quantum physicists postulated the wave-particle duality to unify "wave" and "particle" natures of both light and matter. We raise a question: whether both wave nature and particle nature are primary? For this aim, we design several modern apparatuses and thought-experiments, and carried out some of designed experiments. This book mainly contains two parts: Chapters 12 to 14 report experimental observations; the rest Chapters describe designed Bell-type/GHZ-type apparatuses, 2D-cross-doubl-slits, modified/extended-double-slit, and modified/extended-MZI apparatuses . Based on those apparatuses, we propose T-experiments to study EPR paradox and basic quantum phenomena.To summarize: (1)We propose Extended-EPR paradox to judge whether quantum mechanics is incomplete via determine the physical nature of entangled photons/objects, which is at the most fundamental level. One has to determine the physical nature of entangled photons/objects to completely either prove or disprove EPR paradox. Designed Bell-type and GHZ-type apparatuses/T-experiments to test it.(2)Wave-particle duality: (2.1) Photons/objects behave as particle before passing through double-slit, while behave as particle and distribute as wave after passing through double-slit. (2.2) photons behave as particle before passing through output beam-splitter of MZI; output BS combine two paths of photons into one direction, then photons interfere and distribute as wave. The action of removing output BS in delayed-choice experiment did not send message to source.(2.3) "Particle nature" of photons/objects is intrinsic/primary, "wave nature" is "wave-like distribution" under certain condition and thus, is secondary. (3) Bohr's complementarity principle is Violated. Photons/objects behave as particle and distribute as wave at the sametime in the same experiment. (4)Extended-uncertainty principle: (4.1) Accelerated objects have no wave-like distribution. Accelerated apparatuses (either source or detector) detect no wave-like distribution of photons/objects.(4.2) "New Variable" (Force): To consider the effects of "observation" in quantum mechanics implies to consider the effects of force, a New Variable.(4.3) "New Variable" leads to Extended-uncertainty principle.(4.4) Force/acceleration causes wave function collapse.(4.5) The concept of "reverse of wave function collapse" is proposed.(5) Velocity-dependent of wave-particle duality: (5.1) The wave-like distribution of objects is velocity-dependent. (5.2) For uniformly moving matter, we can always choice a reference frame, such that the velocity of matter is zero, i.e., wave-like distribution disappeared.(5.3) The characteristics of interference pattern of photons is apparatus-velocity-dependent.(5.4) the rules of wavelength variations of photons/objects are conceptually and quantitively different.(6)Cross-double-slit experiments challenge the interpretation of wave-like distribution of photons.(7) Designed several novel modified/extended MZI apparatuses and T-experiments for testing Wheeler's delayed-choi