From where and how the idea of birthday celebration came with cutting of a cake ?

It came from times of starvation - not that long ago. A cake IS life itself when there isn't much food. And the cutting of the cake is the "food sharing" behavior that humans have developed over all these thousands of years of hunting and bringing home the kill.

Cakes are a nice treat, something that you might have only once in a while, maybe to celebrate something. How about celebrating a birthday with a cake? Seems like a good idea.

I mean, yes, you could ask why they don't serve pie, donuts, pancakes, or candy bars instead. But it's just so much easier to make a cake look fancy, by decorating it with frosting, and cakes take a bit more work, so you want to save it for a special occasion.

As for cutting the cake-- how else are you going to serve it to all of your guests? Unless you are willing to let them dig in with their own hands and grab what they want...

The one tradition that I can't come up with an answer for is blowing out the candles. But, you didn't ask about that.

In the U.S., and perhaps in Britain, one makes a wish immediately before blowing out the candles on ones own birthday cake. If one blows out all the candles with one breath, the wish supposedly will come true. The wish is connected with blowing out the candles, not with cutting the cake.

Like wedding and graduations come with a cake its like traditional celebration, of a mile stone for hundreds of years in europe