Banana, apple, orange, dates, all healthy fruits but got sugar. What is the max daily allowance to consume of these for healthy and diabetic person.?

2 and 4 cups. I usually recommend 2 cups of fruits (berries and melons have less sugar than the ones you mentioned) for diabetics and 4 cups for non diabetics daily. Fruits are healthy source of vitamins but can cause weight gain if consumed a lot.
Fruits are healthy. Focus not on the amount of sugar but on how quickly the sugar is absorbed (glycemic index or gi). Foods absorbed slowly (low gi) lead to less Insulin requirement than foods that spike sugar in your blood. Generally fruits are healthy even for a diabetic. Dates, however, do have a high gi. Avoid refined sugars such as cookies potato chips fries white bread sodas-- don't avoid fruits.