A set of tasks appear every six hours and you are free to do them one at a time.  When they are all done your remaining options are to wait six hours or to use the 1k button.

A legendary task appears only rarely so trying to accumulate five hundred completing tasks one at a time would take a very long time and be tedious - that is one of the reasons the option to complete 1k tasks was introduced,

u miss the point

instead of this (i am FORCED to do 1000 task each time )  i can write this  ..my town level is 33 and vip level is 33

I wonder if you have let your VIP lapse? 

I don't think John missed the point.

In their infinite wisdom the gods of the company decided to create a new  quest and partly to make it less tedious clicking tasks they made the click 1000 at a time button.

You would be very  fortunate if you could only click 500 and reach the target, you probably will need many 1000 tasks, to get the 500 legendary that you need.

There is no requirement to get legendary materials or gems.