Nothing in the GDPR states this. It's obviously the intent, but ultimately it's left up to the bon vouloir of EU regulators.
It is perfectly legal under the GDPR to make an example out of you by levying the maximum fine for a first offense, and without warning.
No it isn't. Read Article 83.
[0] https://ec.europa.eu/newsroom/just/document.cfm?doc_id=47889