If all three hosts are in the same cluster, or at least present the same CPU features, vMotion should work as expected. However, keep in mind that - depending on the vSphere version used - your hosts need port groups with the same names, ...
Yes this is no problem. Even if all your hosts where in a different network for vMotion it would work, as long as the network is routable. vMotion across L3 domains is supported these days: http://www.yellow-bricks.com/2015/02/05/new-vmotion-vsphere-6-0/
Based on the above query, Can I set different gateway other then management to my vMotion IP settings.
Will this change my default gateway of Management on setting vMotion into an existing environment