EU citizen retiring to Portugal - health and tax ID registration

Good day,

First off - apologies if I missed the answer to my question in other posts.

The question I have: I am planning to recloate to Porto for my retirement. I will initially stay at a short-term rental (likely an AirBNB) while I look for a home to rent long term or buy.

What criteria do I have to meet before I apply for tax ID and healthcare? Specifically:

• how long after my arrival do I have to wait before applying?
• what documents do I need to bring to prove my residence/address - would an AirBNB booking be enough? And, if it is, how long would it have to be for?
• how often - if at all - do I need to resubmit any documents to prove that I still reside in Portugal? Annually? Every X number of years? Never?
• can I update my address online when I move? I do not know what I will find in terms of accommodations - I may choose to move at some point in the future, to explore/experience other locales in Portugal.

Please kindly point me in the right direction - be it other forum posts or government online resources.

Thank you for your help!