But i mean u see the point, i will try to redesign the code, but if the error occurs again, then this task is doomed for me...

This does not sound right. When I try to run your solution, I get this message:

< Incorrect Result >
latest_clock(0, 2, 2, 2)
 
Submitted: "22:00"
Expected:  "22:20"

Ok, now it is working on test without modifing it, but still randoms just do not go, it writes like "23:08" wrong, needed "23:08".

Your code has a small bug.

The comment in the initial setup says: // The result should be [...] correctly null-terminated. and your code is not doing this.

After deleting one question mark from given in predone tests, it works! But still crashes because i cannot change the random tests that come afterwards... ):

Bruh, The C Translation is imposible, because of the string that waits for 7 chars. (In feedback only 5 chars (12:45), Making C Vatiant imposible, i mean for me...)