I felt like you were talking about my son! He is exactly the same way. EXACTLY!

Thank you all for the answer. He has been in the daycare for the past year and until now he does not say 'hi' or 'goodbye' to his peers. We have to prompt him to say it. This is breaking my heart. I am not sure if it is just a stage that he will grow out of it or something that needs some kind of treatment.

My son is also pretty much like your son with most of the behavior, who is 3.5 yrs old, for some reason he catches only the last 2 or 1 words and repeats in a sentence. Also for 1 word answer, for something like what is daddy's name ? , we need to start sounding first 2 letters like 'Veeeee' for Victor then he kinds of tell it. he labels things, follow few instructions, but still not able to make a conversation yet.

It sounds like he has a lot going for him! Try to focus on that and remind yourself that more great things will come with time and therapy. It sounds like you've set up a good program for him and he's on a really good track. Try not to dwell too much on what he can't do yet and find the joy in what he can do. He will continue to surprise you every day with the amazing things he will accomplish.

As much as you can do. Learn speech therapy techniques and do it yourself in every day life for whatever time you spend with him. Right now, his receptive and expressive language is around 2 years level (I am guessing based on experience but can get a speech therapist to assess). Need to get much further ahead in order to have more meaningful conversations. Try to improve both receptive and expressive speech and build vocabulary first.