Question: Is it necessary to soak rice every time before cooking.What happens if you don't soak rice? Does it effect the taste after cooking? If soaking is necessary then, How much time is required to soak rice?

Answer: 
Rice is going to cook okay even if you don't *soak* it. You do, however, want to wash it until the water runs clear so that you get rid of excess starch and so that it doesn't stick together.

However, if you're worried about arsenic - and apparently this is a thing - soaking the rice would reduce the [arsenic levels](https://www.scientificamerican.com/article/simple-cooking-method-flushes-arsenic-out-of-rice/) significantly. It is not something that's ever kept me up at night, but there are parts of the world where it is worth considering.
I assume you’re not mixing the terms rinsing and soaking:

Rinsing is for geting rid of excess starch on the surface of the rice. This way it won’t be sticky or be less sticky.

Soaking rice does two things:

1. It will, hydrate the rice grains; thus they will cook slightly faster (dry rice also cooks pretty fast)
2. You extract the surface starches into the soaking water. if you discard the soaking water, it will have similar effects to rinsing the rice.