Unable to answer "What are the opening hours here?" – on floor -1: Ταπετσαρίες επίπλων Σπανός (Furniture Store) – osm.org/node/10185804874 via StreetComplete 59.3:

It's a house

Add:
-Pedestrian bridge that connects the upper pedestrian level, surrounding the stadium, with "Esplanada" bridge
-Steps that connect the lower/ground level of the stadium, to the previous bridge
-Footpath(s) that connect the previous steps, with the road close to the roundabout

club=sailing
name=ΝΟΤΚ
full_name="Ναυταθλητικός Όμιλος Τζιτζιφιών Καλλιθέας "
phone=2104810390
website=www.notk.gr
start_date=1958

"Duplicate node"
The place has gone or never existed. A user of Organic Maps application has reported that the POI was visible on the map (see snapshot date below), but was not found on the ground.
OSM snapshot date: 2024-10-17T20:37:52Z
POI name: Κέντρο Εξυπηρέτησης Πολιτών
POI types: office-government
#organicmaps android

http://www.hotelarma.gr/

hotel Avra

"Kalinka" Russian Shop new address (Atlantos 1)
https://rus-kniga.com

πλατεία Εθνικής Αντιστάσεως
oldname: πλατεία Βασιλέως Γεωργίου Β’

5.1 Parallia edem Beach

There's a toilet here

via StreetComplete 52.0