But I assume as the rule says a minimum of 200km EVERY DAY. If I want to go and do 2x 300km days I do not assume I have a days rest.
That original post is 7 years old, and the rule doesn't say that any more.
The current equivalent text:
9.7.1 The minimum speeds are:
- for events registered as 200 to 600 km – set by the organiser within the range 14.3 to 15kph;
- for events registered as 700 to 1200 km - 13-1/3 kph;
- for events registered as 1300 to 1800 km - 12 kph;
- for events registered as 1900 to 2400 km - 10 kph; and
- for events registered as 2500 km and over - 8-1/3 kph.
So your only question now is, how much time flexibility do you have at intermediate stops (controls)? Personally I think it's quite ridiculous to even think about passing times at unstaffed (includes all DIY) controls, but that's not the official view. That said, I don't see a very long bike ride as an excuse for a serial sleepover (disclaimer, never done more than 1400km).
Looking at the 1000km question, the time limit is 75h (for exactly 1000) under the current regulation, but was 75h12m under the old regulation quoted in the OP.
The (hypothetical, I hope) 2498km would surely be 'registered as 2500' and not as a 2400, and so would have a time limit of 300h.