The normal PR (ie not via ARI) requires physical residency in the country (more than 183 days/year) for at least 5 years plus several other requirements, see https://imigrante.sef.pt/en/solicitar/residir/art80/. These requirements are consistent for all EU countries.
A2 is the language requirement.
For citizen applications, you may want to read the following:
https://irn.justica.gov.pt/Impressos-e-Modelos). In Portugal, IRN is responsible for assessing applications for citizenship. The information is only in Portuguese. Right click, choose translate, for another language.
A Nomad poster has also provided a helpful long read here - a little further up on this thread.
https://community.nomadgate.com/t/portuguese-citizenship-application-after-5-years-of-golden-visa/21226/45?u=onward
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