
The provided sources do not contain information on how Jeetendra got the nickname 'Jumping Jack'.
Jeetendra starred in the 1967 film 'Farz', which was a turning point in his career. He also appeared in the 1970 film 'Mere Humsafar' with Sharmila Tagore.
Based on the available information, there is no indication that Jeetendra will make a comeback to acting soon.