Abstract:  In the classical unification scheme, type-1 (broad-line) AGNs are depicted as unobscured accreting supermassive black holes with similar face-on viewings of the circumnuclear optically thick tori. However, the dust SEDs of these systems can have significant variations, as seen among, e.g., the hot-dust-obscured galaxies, extremely red quasars, and hot-dust-free quasars, that cannot be easily explained in a uniform picture. In this talk, I will introduce a semi-empirical framework that has successfully reconciled the IR SEDs of type-1 AGNs seen at z~0 to z~6. In contrast with the complicated numerical torus (+polar dust) models, our simple approach greatly reduces the model degeneracy and provides useful insights on the possibly diverse dust environment among different populations of type-1 AGNs. Combining the knowledge of AGN SED variations with other techniques, such as mid-IR dust reverberation mappings and SED decomposition techniques, I will also talk what constraints we may put on the AGN torus structures and the possible features of z～5-6 quasar host galaxies.