Other than AP being considered as an OBE, the other topics you mentioned should not be considered the same. Here is a brief explanation of each below.
Astral projection (or astral travel) is an interpretation of out-of-body experience (OBE) that assumes the existence of an "astral body" separate from the physical body and capable of traveling outside it. Astral projection or travel denotes the astral body leaving the physical body to travel in the astral plane.
What is the astral plane? The astral plane, also called the astral world, is a plane of existence postulated by classical (particularly neo-Platonic), medieval, oriental and esoteric philosophies and mystery religions. It is the world of the planetary spheres, crossed by the soul in its astral body on the way to being born and after death, and generally said to be populated by angels, spirits or other immaterial beings.
Remote viewing (RV) is the practice of seeking impressions about a distant or unseen target using subjective means, in particular, extra-sensory perception (ESP) or "sensing with mind".
Typically a remote viewer is expected to give information about an object, event, person or location that is hidden from physical view and separated at some distance. The term was coined in the 1970s by physicists Russell Targ and Harold Puthoff, parapsychology researchers at Stanford Research Institute, to distinguish it from clairvoyance.
An out-of-body experience (OBE or sometimes OOBE) is an experience that typically involves a sensation of floating outside one's body and, in some cases, perceiving one's physical body from a place outside one's body. Astral projection is considered a for of an OBE.
An NDE is a near-death experience, the perception reported by a person who unlike the others, only happens when a person has nearly died or who was clinically dead for any given period of time and revived.
Personally yes I do believe that all of the above experiences are possible. I personally have experienced remote viewing and was later able to confirm that what I witnessed during this experience was accurate. But I did not set out to have this experience purposely. It actually happened by accident while I was attempting to go to sleep but never quite fell asleep completely. Yet I can't say I was fully awake either. It's sort of an inbetween state of conscienceness is the best way I can describe it. Also incase you are unaware, there is risks to anyone who is successful in having these experiences. So anyone attempting to achieve any of the above experiences, please do research regarding the dangers/risks of such tasks BEFORE attempting to do so