The Bellman-Ford algorithm determines the shortest path from a source $s$ to all other vertices. Initially the distance between $s$ and all other vertices is set to $\infty$. Then the shortest path from $s$ to each vertex is computed; this goes on for $|V|-1$ iterations. My questions are:

• Why does there need to be $|V|-1$ iterations?
• Would it matter if I checked the edges in a different order?
  Say, if I first check edges 1,2,3, but then on the second iteration I check 2,3,1.

MIT Prof. Eric said the order didn't matter, but this confuses me: wouldn't the algorithm incorrectly update a node based on edge $x_2$ if its value was dependent on the edge $x_1$ but $x_1$ is updated after $x_2$?