Dieser Bereich kann Inhalte enthalten, die nicht für alle Nutzer geeignet sind. Dazu können unter anderem Texte, Medien oder Diskussionen gehören, die als beleidigend, extremistisch, gewaltbezogen oder anderweitig belastend empfunden werden. Wenn du solche Inhalte nicht sehen möchtest, nutze bitte die jeweiligen Filter- und Meldeoptionen der Plattform oder meide entsprechende Threads/Communities.
for blue signs it’s not the shape that matters. a blue sign with an arrow is always a must. circular ones indicate what you need to do in your current lane (eg “keep right”), square ones on a lane you could turn onto (eg “the crossing road is one-way in this → direction”)
It absolutely is the shape that matters. A blue circle with an arrow indicates you MUST follow it, a blue square with an arrow indicates you CAN follow it. A blue circle with an arrow pointing forward can be replaced with a red circle with arrows pointing in every other direction, because it indicates a mandatory, I.e. you must eat the banana.
it varies. france and norway have some square mandatory “keep <direction>” arrows and sweden has the aforementioned “one-way in your direction” square arrow.
No, in general the shape 100% matters. Rectangular signs (not to be confused with supplementary plates) are almost always purely informational, with the singular exception that you mention (“one way” which is regulatory). See also: https://www.gov.uk/government/publications/know-your-traffic-signs/regulatory-signs
idk if using the uk in particular as an example there is very useful.