You are WRONG, Crispin. What you are descriobing are red lines set by the West. Joe Biden was the one who said we cannot send tanks, that it was a red line. Putin never said that. Biden said that sending F-16s was a red line. Putin never said that.
Scholz and Germany started out sending only helmets. Sending German tanks was a red line, it was a bad look, given what the Germans did to the Russians in WWII., Scholz said. But Putin never said that.
In short, it was always the West, and especially the US, who set their own "red lines" and then overstepped them..
In fact, it is the stuff of jokes about how Biden constantly said that "X" woudl mean WWIII and then a ferw months later agreed to "X".
I defy you to show me a quote where a Russian described tanks and planes as red lines. In fact, the only reaction the Russians said about sending Leopards and Abrams tanks were that "they will burn like all the rest".
Likewise, F-16s were not a problem, Dmitry Medvedev said that they would be destroyed as soon as they entered Ukrainian air space. And they have. It was never a red line for Russia.
No. The red line was always NATO in Ukraine. Hell, Russia doesn't even care about all the French and Polish troops fighting in Ukraine. And they just post videos of al the Western "mercenaries" fighting there. No red lines about that.
So do not be fooled. Putin rarely issues a red line. And the US/NATO-fired missiles is one.