3rd endless mode

The third endless mode is another endless mode (also being the last checkpoint in the entire game (If you don't count any hypothetical loops of endless mode), preceded by the 2nd endless mode.
 * It is reachable at 28,000 distance. However, this won't have an ending, or even lead to the 4th endless mode, as the Repeating Room Glitch will occur past a distance of 30,000 or stage 30 (score of 100,000 = stage 100) (2nd stage harder variant).
 * If you did the Random Rooms Glitch, it will be re-doing the same room (only one room) over and over again (which will be stage 30).

Only a dozen players have reached this, according to the Smash Hit page.

It is possible to reach the 3rd endless mode without the Random Rooms Glitch. It is also possible to 'complete' third endless mode, i.e. reach stage 30, normally. It can be done most easily if you stash on 1,100 balls or more, which can only be accomplished by using the Ball Grinding Method, a very lucky Room Generator, or by getting a bit lucky and absolutely conserving balls as much as possible. This is easier to accomplish on mayhem mode as you get a pretty large boost in your ball count in the boss rooms. This is very strict, however, so expect to do multiple runs.

Evidence
 Evidence of reaching third endless mode from normal gameplay: 
 * https://www.youtube.com/watch?v=0Hl-3M8XSDU (distance 35,551) (unplayable due to closed YouTube account, this was mentioned at one point)


 * MRK GAMES: distances of 32247 and 34558 have been reached, entering third endless mode using only standard gameplay. Videos: https://m.youtube.com/watch?v=YUuDV2KhTHw, https://www.youtube.com/watch?v=MRvMnhNDPEw&lc=UgzKXqFxpA_COdxlIIZ4AaABAg

 Evidence of reaching stage 30, i.e. the 'end' third endless mode, from normal gameplay: 
 * Benjamin Thoburn: third endless mode is again reached using standard gameplay. Video: https://m.youtube.com/watch?v=jmECbHYApPI


 * Benjamin Thoburn: Stage 30 (repeating infinity/'checkpoint 15') has been reached from playing through the game normally. Final distance 35819. Video: https://www.youtube.com/watch?v=az0NOYmc7NA

GlitchLord

 * Reached a score of 35100 with the Random Rooms Glitch. See here: Checkpoint_5
 * The comment says:
 * "what??? checkpoint 13??? i have never got to checkpoint 13, there are checkpoints 0,1,2,3,4,5,6,7,8,9,10,11, infinity. If infinity is checkpoint 12, then there isn't a checkpoint 13. 5-5 is a fake level. My highscore is 35100 and if you use [the random rooms] glitch abuse you can get my score."

MondaysAreTheWorst (as of 26 January, 2020)

 * Rached 29310, beating the previous score of 28731 in Training Mode, it is the former world record of training mode.


 * Reached the score of 28258, beating 28080 in the Classic Mode.
 * Reached the score of 40543 in Mayhem Mode. It was previously 36000 (which was mentioned on a comment)

Tia'a Chon Ming

 * 32329 at mayhem, 25361 at normal, and 21039 in Training (comment here)