Can I have both vCenter 5.5 and 6.5 servers in one vSphere?
And can I export my Distributed Virtual Switch config from vCenter 5.5 and import it to vCenter 6.5?
Would doing so crash my vSphere or cause any other problems?
what do you mean in one vsphere? do you mean 5.5 and 6.5 hosts in one vcenter?
this article should explain more on mixed versions.