Hi and welcome to Drawspace.
Photorealistic drawing is generally done from photographs simply because of the time required to complete a competent image in that technique. It can be done from life to get the likeness/landscape, etc., but for details you would need a lot of time in close observation, so a combination of the two would be required. Terry Redlin and Thomas Kinkade provoke different responses in different people. They are representational artists, but not photorealists in my opinion. A photorealist who I had the pleasure of doing a class with was
Armin Mersmann. Armin is one of those who I would call a true photorealist artist and he uses photos for the reasons outlined.
Whether you can draw photorealistically without references or from life, is that what you're asking? If so, I would say no. To draw anything from memory gives a twisted view as you have to rely on your mind to provide the image and your mind's image will likely be very different than reality and be swayed by different exposures to subject matter and your own interpretations of them.
I don't know of any artists who can create a photorealistic drawing from memory. Yes, some can draw interpretations of various identifiable images but without a reference or real life subject, it would be nigh impossible to put that level of information on paper. You would need to have intimate knowledge of a subject and have completed thousands of drawings of that same subject to be able to create every value, highlight, crease, crevice, etc. to make it a photorealistic drawing.
Practice of course will help you build information about how light affects objects and how techniques are used to create the shapes that you want to represent. All artwork is based on reality. The fantasy pieces are simply morphed into different shapes and colours to create a new image that your mind helps evolve. Its the same principle as in cartoons such as anime. You need to know anatomy and how the body moves, facial expression, how lighting affects clothes, hair, shadows, etc. Only then can you safely change or characterize the individual into something else. The same applies to the landscapes that Kinkade for instance, paints. He may have a concept, then would likely find reference images or real life places to sketch thumbnails, set up composition, lighting etc. Then he can go in and create the images that he does.
I'm not sure if that answers your question or not. My comment in any form of drawing is to simply practice. Use reality as your base and learn traditional techniques of how to apply mediums to supports. Explore by all means, but realize your limitations are based on your ability and your perception of imagination and reality.