Corruption on hardmode

So I have 2 questions: 1: Will the wall hold off the corruption (the wall is wood, stone brick, stone brick and wood) 2: What are the chances of corruption spawning (when I enter hardmode) on the other side of the wall?

Solution 1:

1: Your wall will prevent the Corruption from spreading from one side to the other, yes. Wood and Gray Brick are incorruptible (even in Hardmode), and 4 blocks is the recommended wall width for preventing its spread.

2: There is, however, a chance that either Corruption or Hallow will cross your wall when Hardmode begins. The game will convert large sections of your map into Corruption and Hallow as soon as the Wall of Flesh is defeated, which may span across both sides of your wall. Additionally, each time you destroy a Demon Altar, a small pocket of Corruption or Hallow will appear in a random location on your map, and spread from there. This could happen on either side of your wall, or within the Jungle itself.

If your aim is to protect your Jungle, I would suggest using powders to neutralize any conversions made there upon engaging Hardmode, and refrain from destroying any Demon Altars on this map.