3. There will be one more button Start, clicking start button those two jobs should start running in the background.
7. After clicking 'start' button, the text on it should change to 'stop'. And then pressing 'stop' it should toggle back to 'start' and accordingly the job status should also change to 'Stopped' from 'Running'.
... need help on #3 to #7."
I provided code showing button creation, callbacks and changing widget text.
I also provided documentation links.
What exactly do you need help on?