You must be more precise on what you want to do.
I'm afraid that you won't find any 'clock' doing this.
You must doing it on your own by code with a diplay and timer(s).
For your backward clock, use a timer and count backwards.
For the chronometer use a timer, with a 1 second interval, and add 5 each time.
But without knowing exactly what kind of clock or chronometer you want to do it is difficult to give you the best advice. It will also depend on the precision you need or want to achieve. Then you must manage the clock or chronometer with the activity lifetime, for example if your program is supposed to work in both orientations.
Best regards.