Old MCPE World Bug

In quite a few of my older worlds from 0.7.1 and bellow have issues with mobs but more importantly loading some areas of the world. All of the blocks are there but do not properly render, placing blocks does not help either. The only way to see those blocks is to make the world infinite. The problem with that is making it infinite only works for some worlds the others just crash my game. In some cases with those worlds is they have become potentially permanently damaged invisible bedrock in places it wasn't before. Going into some invisible areas may cause very bright flashing lights and the only way to escape it is to teleport out of it. The videos below show some of the issues I have experienced