Why do the completed bricks in renko charts retrace during price reversal and up to what point can the retracement happen?

The retracement in Renko charts can occur all the way back to any bar in the current selected chart time frame. Bars from prior periods will always remain permanent (fixed). So, until the selected chart period is complete, the bars within the period will be recalculated as new data comes in, and Renko bars will be plotted accordingly.