So yesterday I saw that you could play old versions of Minecraft. I tried out Beta 1.0 and played for about 5 minutes. I got bored and switched back to 1.6.2, and now many Beta visuals are still there, i.e no Smooth Lighting, different looking leaves, whole furnaces light up, different grass color, etc. etc.

What I expected to happen was...:
I thought I would be able to switch back to 1.6.2 with no problems at all.

What actually happened was...:
Many Beta visuals were still there.

Steps to Reproduce:
1. Create a new profile and play Beta 1.0.
2. Create a world and play a little while.
3. Go back to 1.6.2 and see Smooth Lighting gone.