It this game setup to play the entire battle from day one through to victory or defeat? Or is it only designed to play individual scenarios.?

It's a series of individual scenarios where your options depend on the scenario you just played and the victory locations you control. After a battle, both sides are presented with strategic options for attacking or defending, and the map is selected based on that. For example, if the union controls Oak Hill, then they can choose to defend the hill, or pull back to Seminary Ridge. On the other hand, if the union controls Herr's Ridge, then they can take a more aggressive stance. Forces carry over and losses are permanent, so force preservation is important.