Thank you so much. Your answer is very helpful. It is because my number got current. I know that although the numbers get current, getting interviews also unpredictable. Again thanks so much for the answer to my third question. He is worried about the submitted DS 260 since he will be planning the STEM OPT and I was blaming myself for the mess. If I have found these informative websites I would not have done so. I appreciate your answer @Sm1smom.1. This was answered before. You must complete CP and enter the US first before your son can file for AOS as your derivative.
2. You do not have to write anyone or anywhere.
2b. The demonstrated immigrant intent should not impact OPT or grand school while he remains in the US. The impact of the declared immigrant intent comes into play if he departs from the US and needs to apply for a new NIV from the embassy (outside the US) to enable him return to the US.