Unable to answer "Who is allowed to use this playground?" – Playground – https://osm.org/way/503445799 via StreetComplete_ee 57.0:

Doesn't appear to be a playground here in the traditional sense, just dining tables for the patio area. However there is a patch of grass surrounding the patio.

Attached photo(s):
https://westnordost.de/p/202362.jpg