Give an example of 2 non isomorphic regular tournament of the same order
I tried so many tournaments of the same order but got no luck, if they are regular, meaning all vertices of them have the same in and out degree, so they have arc preserved, which end up to make them isomorphic. I'm not sure there are such tournaments exist.
According to the data at http://cs.anu.edu.au/~bdm/data/digraphs.html, there is only one isomorphism class of semi-regular tournaments on five vertices, but there are five classes on six vertices and three on seven. (The tournaments themselves are there, the three on seven are regular.)
[This is a corrected answer, as indicated by Brian M. Scott.]