I can only play 1 Version Of MC.

My cousin made a MC server and I have been trying to get on i, but every time that I go on my MC crashes. I can go on any servers in 1.8, but not 1.7.10 or 1.7.9. I haven't really tried anymore versions but, I feel that it is the versions of MC. Please help me, I am so confused y I can only play 1 version of MC