Clearly, any prime between $50$ and $100$ can only be adjacent to vertex $1$ and hence has degree $1.$ Also, every vertex has degree at least $1$ since vertex $1$ is a neighbour of everyone. This also implies that $1$ has the highest degree of $100-1.$
Diameter is $2$ because from vertex to any other vertex, we can have a path of length $2$ via vertex $1.\; \text{G}$ is connected because vertex $1$ is adjacent to everyone.
