Lal:
Thank you once again for clarifying some of my doubts.
I think I finally understand why the Buddha said: Sabbe sankhara annica, Sabbe sankhara dukkha, Sabbe dhamma anatta, and not Sabbe dhamma annica, Sabbe dhamma dukkha, Sabbe dhamma anatta.
Sabbe/Sabba as I understand it is the Pali word for all (without exception). All sankhara (even those initiated just to maintain life or to compassionately help others) have annica, dukkha (especially sankhara dukkha) and anatta nature. All dhamma have anatta nature. I think some dhamma (but not all) have annica and dukka nature. Therefore the Buddha did not teach Sabbe dhamma annica, Sabbe dhamma dukkha.
What are those dhamma that have annica and dukkha nature?
(Here can I use dhamma to refer interchangeably to rupa above the suddhastaka level as well?) Those dhamma that have dukkha nature are our bodies. Even Buddhas and Arahants have bodies subject to dukkha. Dhamma that impinge on our mano indriya to impart dukha vedana (as a result of previous immoral actions) are also of dukkha nature.
Yet some dhamma that impinge on our mano indriya which happens when some stray thoughts come to our mind impart upekkha vedana. These dhamma do not have dukkha nature, I think.
Those dhamma that have annica nature are those that we react with clinging and longing to, I think. These same dhamma will inevitably have dukkha nature as well, when they fail to satisfy us. For example, we may recollect a satisfying meal we had for lunch, and immediately savour that moment in our memories for quite some time, only to be jolted from our reverie by pressing daily issues that demand our attention. Thus our disappointment at being interrupted may linger for a while, and we may brush it off as a normal state of affairs, failing to recognise its dukkha and annica nature.
Yet for other dhamma that impinge on our mano indriya, for example the sight of a familiar name triggering a memory of a distant relative one has neutral feelings for, one will not cling to the memory and it does not have annica nature for us.
By the way, you have mentioned that everything falls under four categories: 1) citta; 2) cetasika; 3) rupa (which includes dhamma which are basically just rupa below the suddhastaka stage); 4) Nibbana. Which of the four categories does sankhara belong to? Are they cetasikas?
Thank you very much in advance for your answers to my questions. I hope that I have not been rambling or bringing up old material repeatedly, and caused annoyance to anyone in the process. Please do tolerate this if it happens unintentionally.