I wasn't sure what you meant by this - are you asking if you need to give authorship to all participants? (If so, no).

Or are you saying that analysis from your dissertation that you want to publish in additional papers should include all participants? If so, you should be analysing based on all participants relevant to the question/focus/topic of your paper, but you don't have to include data from them for the sake of it, or to inflate response rates or similar.

Your data should tell a story to answer a specific question or expand upon or explore an idea. In which case with a large, rich, dataset of qualitative transcripts you're analysing across that source (using a particular choice of analysis or theoretical framework) rather than on a participant-by-participant level.

This means for some papers or presentations the things some participants say, or the meanings you draw from their ideas or words will feature more than others. So long as you're not cherry picking ideas, ignoring or deliberately excluding relevant data, or only referring to the ideas of one person while passing it off as more, the focus should be on what flows through the transcripts or texts you're analysing.

Not necessarily. It depends on your research methodology, ethical considerations, and the specific requirements of the journals you're submitting to. However, it's typically good practice to acknowledge and properly cite all participants who contributed to your dissertation research in some form.