Selectively actuating expandable reamers and related methods

An expandable reamer for use in a borehole in a subterranean formation, comprising:

• a housing defining a central bore;
• a plurality of blades carried by the housing and movable between a retracted position and an extended position responsive to flow of drilling fluid;
• a sliding sleeve disposed within the central bore and coupled to the housing, defining an axial fluid passageway, and comprising at least one port in a sidewall of the sliding sleeve, the sliding sleeve being movable between a first sleeve position and at least a second sleeve position to alter flow of drilling fluid;
• and
• a seat disposed within and coupled to the sliding sleeve, the seat being movable between a first seat position and a second seat position to alter flow of drilling fluid,
• wherein the expandable reamer is configured to operate in a first, retracted state in which the plurality of blades is in the retracted position when the sliding sleeve is in the first sleeve position and the seat is in the first seat position, to operate in a second, extended state in which the plurality of blades is movable to the extended position when the sliding sleeve is in the at least a second sleeve position and the seat is in the first seat position, and to operate in a third, retracted state in which the plurality of blades is returned to the retracted position when the sliding sleeve is in the at least a second position and the seat is in the second seat position.