Board Thread:Questions and Answers/@comment-31625365-20170329135349/@comment-26377724-20170329194153

Maybe you can try to see the chart to have a complete view of the events at this page: Timeline

1) Suzuha knows her mission indirectly from her father through the Valkyrie resistance group. She also knows the phenomen of the attractor field convergence, whatever she can say to okabe or other members she can't change the past by herself. She also knows that okabe is the co-founder of the resistance and involved in the fabrication of a time machine, the IBN doesn't surprise her, at this moment she knows her mission will be a success. (On a side note she is trying that in a manga by telling kurisu she will try to kill her in the future, that change nothing to the fact she failed).

2) Kurisu is needed because we need her to contain and contest nakabashi. In other words discredit him and his allegations about a time travel theory.

And the steins gate worldline is between bet and alpha in order to share some properties of both attractor field, in other words, the 1% scale for attractor field isn"t exactly 1%.

And Yes Zero is full part of the main story of steins gate, it's a midquel in reality.