carlosdev: my question is, after completion of my 500 ranked rounds as legend, will my scoring pattern of average reset and scoring 29 will make much difference of average dropping down or it will be the same as before?
It doesn't reset then, but counting will be a tad different, because the number of 500 scores stays constant.
As Jim pointed out, any (and only) scores better than the highest in the mix will replace the highest and thus modify the average. That .23 drop equals a score difference of 0.23*500 = 115 which is incredible, pointing to a 170+ score in the mix.
As any high scores are being replaced, the per-game effect will cease. In the end, each shot stripped, e.g. a 62 replacing a 63, will modify the average by 1/500 = 0.002 - invisible due to the rounded display. This is what I call the effect of the big denominator (500).
It's a grind for sure - keep up the fun of the game!