1
There is a dataset of athlete details on kaggle.com that shows most of what you ask for at point 1 above (age, nationality, height, weight – although not birthdate) as well as the events that they participated in and what medals they got (if any). The data was scraped from sports-reference.com and is shown on Kaggle as being CC0 licensed (probably on the ...
1
I think the Nager.Date API meets your requirements.
the model have both localName and name
https://date.nager.at/swagger/
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