can´t open the Version 1.7 (only 1.8.1)

I can´t open any versions of minecraft. I only can play on the version 1.8.1. If I change it, it crashes

I only wanted to play on version 1.7.9

What actually happened was, that it crashed

Steps to Reproduce:
1. I changed the version from 1.8.1 to 1.7.9
2. I opened Minecraft
3. After I click on a multiplayer server, it crashes