I would be slightly more concerned with these behaviors as they relate to the possiblity of an autism spectrum disorder. I'm a speech pathologist specializing in autism and these types of errors are not common in typically developing children or in children with other developmental delays. They are often hallmarks of autism. It may be too early to arrive at a definitive diagnosis as it sounds like he's demonstrating only some mild concerns, but it's definitely something to keep in mind as a possibility as you observe his development. It would be a good idea to begin a relationship with a pediatric neurologist, psychologist, and/or speech language patholgist who focus on autism and your local school district so that you can continue to monitor your son's development. Many times with children who are diagnosed with Asperger's or who are only mildly impacted by autism, the social deficits do not appear until they are in a group setting with other children, like a preschool program. You may wish to get him involved in such a program so that you can see how he does and provide him with any support that he may or may not need. Best of luck to you.
Yes, this is entirely normal.
I am only concerned about him sometimes confusing pronouns - only in situations I described in the previous post - and him not asking why questions. He will ask what, where, and who questions, but no why or how questions. Oh, and one more thing I find strange. When I ask him yes/no questions, he will say no if it's something he doesn't want, doesn't want to do etc., but if the answer is yes, he sometimes won't say yes. For example, if I ask him "Do you want to go to the park?" He will respond, "Want to go to the park." or "I want to go to the park." When he responds with "Want to go to the park" he's not repeating it back as a question, it is a statement. Or if I ask him "Do you want to get some ice cream?" he'll say "Want to get some ice cream!!" as a response, not repeating it as a question. Is it normal for children to respond to questions this way to yes/no questions?
Based solely on this particular behavior, there is no reason to suspect any condition along the PDD spectrum, autism or otherwise. It is not unusual for a pre-school age child to use pronouns in this way. Do you have any other reason to be concerned about the course of his development?