In its many embodiments, the present invention provides certain iminothiadiazine dioxide compounds, including compounds Formula (I): and include stereoisomers thereof, and pharmaceutically acceptable salts of said compounds stereoisomers, wherein each of R1, R2, R3, R4, R5, R9, ring A, ring B, m, n, p, -L1-, -L2-, and -L3- is selected independently and as defined herein. The novel iminothiadiazine dioxide compounds of the invention have surprisingly been found to exhibit properties which are expected to render them advantageous as BACE inhibitors and/or for the treatment and prevention of various pathologies related to β-amyloid (“Aβ”) production. Pharmaceutical compositions comprising one or more such compounds (alone and in combination with one or more other active agents), and methods for their preparation and use in treating pathologies associated with amyloid beta (Aβ) protein, including Alzheimer's disease, are also disclosed.