Short answers, pulled from the story.
The Pali tradition defines all existence through three characteristics: impermanence, unsatisfactory nature, and no unchanging self. These marks appear as sabbe sañkhārā aniccā, all conditioned things are impermanent, and all dhammā have no soul.
The northern Buddhist Sarvāstivāda tradition presents a distinct set including four characteristics known as the four seals of the Dharma. Their version describes Nirvana as calm or peaceful while maintaining that all compounded phenomena are impermanent and all dharmas are non-self.
Nārada translated these verses in his work on The Dhammapada published in 1978. This translation covers Dhammapada Verses 277, 278 and 279 which teach that all beings conditioned by causes are impermanent and suffering.
Ignorance regarding the three marks serves as the first link in the process of sañsāra because it subjects a being to repeated existences in an endless cycle. Dissolving that ignorance through direct insight brings an end to sañsāra and its resulting suffering according to the Four Noble Truths.
Dukkha means unsatisfactory and is commonly translated as suffering or pain within the context of the First Noble Truth. Mahasi Sayadaw calls it unmanageable and uncontrollable by any will, covering birth, aging, illness, and death as inherent parts of existence.