Q.Flowers of chiku tree wither away
Flowers of chiku tree do not turn into fruit. They just wither away. Can you suggest some remedy?

How old is your sapodilla (chiku) tree? Seedling trees bear fruit in 6 to 7 years or more. Grafted trees may begin to bear fruit in the second to fourth year after planting.
Do you know which cultivar you have? The UFL site for Sapodilla trees suggest that some cultivars can self-pollinate, but others not (http://edis.ifas.ufl.edu/mg057).
For the time being, I would double-check the care of your sapodilla with regards to your watering schedule and fertilizing at the following link:
https://www.gardeningknowhow.com/edible/fruits/sapodilla-trees/growing-sapodilla-fruit.htm