An apparatus (23, 23C, 23F, 231, 23S, 23T, 23V, 23Z, 128) for forming at least one manifold string usable with an upper end manifold to subterraneanly control a plurality of fluid mixture flow streams within or between one or more reservoirs during a plurality of reservoir operations, wherein the apparatus comprises: at least one intermediate manifold crossover or a reservoir fluid radial passageway disposed between an upper end of a plurality of conduits (2, 2A, 2B, 2C, 2D, 39) and a lower end of the plurality of conduits for forming stationary conduit pressure barriers that are disposed within a casing barrier and an associated surrounding casing passageway through subterranean strata, wherein said associated surrounding casing passageway is excluded from a reservoir flow by a lower end isolation, thereby forming said at least one manifold string and an associated plurality of stationary conduit pressure barriers to reservoir flow between an upper end wellhead manifold and said lower end isolation, and wherein reservoir fluids are flowable through an inner passageway of said plurality of conduits and at least one concentric intermediate passageway surrounding said inner passageway to and from at least one fluid control device (61, 128), characterized in that said at least one fluid control device is positionable along and selectively disposable across, and removable from across, said inner passageway to subterraneanly cross-over said plurality of fluid mixture flow streams radially inward or outward through said reservoir fluid radial passageway, wherein said fluid mixture flow stream crossover occurs between at least two of: said inner passageway, said at least one concentric intermediate passageway, and a surrounding passageway to, in use, selectively control and access at least one portion of a fluid mixture flow stream from at least one of said reservoirs, wherein the plurality of fluid mixture flow streams are communicated to and from a proximal reservoir region during said plurality of reservoir operations. at least one intermediate manifold crossover or a reservoir fluid radial passageway disposed between an upper end of a plurality of conduits (2, 2A, 2B, 2C, 2D, 39) and a lower end of the plurality of conduits for forming stationary conduit pressure barriers that are disposed within a casing barrier and an associated surrounding casing passageway through subterranean strata, wherein said associated surrounding casing passageway is excluded from a reservoir flow by a lower end isolation, thereby forming said at least one manifold string and an associated plurality of stationary conduit pressure barriers to reservoir flow between an upper end wellhead manifold and said lower end isolation, and wherein reservoir fluids are flowable through an inner passageway of said plurality of conduits and at least one concentric intermediate passageway surrounding said inner passageway to and from at least one fluid control device (61, 128), characterized in that said at least one fluid control device is positionable along and selectively disposable across, and removable from across, said inner passageway to subterraneanly cross-over said plurality of fluid mixture flow streams radially inward or outward through said reservoir fluid radial passageway, wherein said fluid mixture flow stream crossover occurs between at least two of: said inner passageway, said at least one concentric intermediate passageway, and a surrounding passageway to, in use, selectively control and access at least one portion of a fluid mixture flow stream from at least one of said reservoirs, wherein the plurality of fluid mixture flow streams are communicated to and from a proximal reservoir region during said plurality of reservoir operations.