Both the top and bottom landing at stairs needs to be at least 36 inches deep. IRC 311.76

The maximum vertical height between landings/ floor levels without another landing is 12 ft 3 in. IRC 311.73

Interior stairs are required to have a light switch at each floor level, both bottom and top if more than 6 risers/steps. IRC 303.7

Handrails are required on at least one side if more than 4 risers/steps. IRC 311.7.8

The top of the railing is to be 34 to 38 above the nose of the step. IRC 311.7.8.1

The rail must not project more than 4 1/2 in into the stairway. IRC 311.7.1

The rail needs a minimum space from the wall of 1 1/2 for your hand to grasp the rail. IRC 311.7.8.2

The vertical rails/spindles/balusters are to have openings of a maximum of 4 inches. This is to prevent a 4 inch diameter sphere from passing through. This is primarily for child safety. IRC 312.1.3