I haven’t found a thread or FAQ about uninstalling prior versions and releases of ZBrush. When 3.5R2 came out, I was told not to uninstall 3.1 because when 3.1 support was discontinued, it couldn’t be reactivated. In addition for each new release, the install does not effect the prior installs (I have 4 different releases instead of the older install being replaced with the newer one).
Is there a chart that shows the addons for 3.1 and 3.5 that have not been ported over or incorporated in the newer releases of ZBrush.