Paticca Samuppada can be understood at different levels. Only a Buddha can understand it fully, and be able to explain any worldly phenomenon.
But one needs to understand at least what types of abhisankhara lead to births in various reams.
– In particular, one needs to understand what types of abhisankhara can lead to rebirths in the apayas, “good realms in kama loka”, and in Brahma loka. Those are apunnabhisankhara, punnabhisankhara, and anenjhabhisankhara.
– Then one needs to be able to figure out what each of the steps involves.
Each person’s learning curve is unique. Thus, I cannot say to read this first. You should start reading the following section;
“Paṭicca Samuppāda”
Generally, I would say start at the top.
I would say to get a better understanding of Paticca Samuppada first. Then you may be able to answer your other questions yourself.
– Also, the Four Noble Truths, Paticca Samuppada, and Tilakkhana are interrelated and interconnected. You will also see that when getting to the basic understanding.
Some people may find it is better to start with the following section:
“Basic Framework of Buddha Dhamma”
I cannot point out specific posts, because I have no idea how much you or anyone else knows. Don’t get frustrated. Just work at it. Obviously, you have made progress and you are making progress.