I think the RaW say that for an investigation sequence

1. the GM determines the investigation complexity

2. players roll their Investigation Skill against the difficulty associated with the investigation, with each success subtracting Int (B) + 1d10 hours from the total time determined by the complexity.

Do I have this Right?

Also, the book labels a set of skills as part of the investigation subclass. Could all of those be used for investigation rolls above?

Investigation tests require players roll applicable skill rolls until test time is reduced to 0.

Whether a skill is applicable is ultimately up to the GM, but yes, skills in the investigation sub-class are typically applicable.

Investigation skill rolls may be assisted like normal.

Individual skill rolls can have these effects (not cumulative):

• Success (regardless of #DoS reduces investigation test time by -(d0+CharBonus) hours.
• 1-2 DoF means the investigation test time is unchanged.
• 3-4 DoF increases investigation test time by +d0 hours.
• 5+ DoF resets the investigation test progress & complicates the investigation test by +2 steps (see table 7-4 on p.186).

If the test is reset, any time left on the first attempt is time wasted by Acolytes faffing about.