How U determine first and second reflection points

Don't overlook 1st reflection points on the floor and ceiling! Depending on the type of surfaces and their shape they can be just as important as the side walls, albeit the ceiling reflections can be tough to deal with. If you treat the 1st reflection points properly you really shouldn't be too concerned by the second reflection points. IMHO.

I'm not sure what you are trying to say, but if you are saying that you need all of the reflections from the walls, ceiling, and floors to get 3d effect, you are overlooking the fact that on well recorded software that information is already there. To not treat the critical reflection points will distort the original signals and you will lose the value inherrent in making recordings using minimal mic'ing with realistic spatial information. In other words, there goes your depth of field everyone seems to think is so important.