Controlling fast particles in tokamaks is crucial for both safe device operation and optimal plasma performance. We report the first observation, on EAST with a fully metallic wall, of a central ion temperature peaking (Ti-peak) regime reaching 9 keV, achieved through the synergistic combination of high-power neutral beam injection and argon (Ar) injection. Within this Ti-peak regime, we observe multiple instabilities spanning different scales, including fishbone (FB), long-lived mode (LLM), beta-induced Alfvén eigenmode, and ion-scale turbulence. Notably, the presence of FB and LLM instabilities is associated with a suppression of ion-scale turbulence and a flattening of the core current density profile. Furthermore, edge fast-ion-driven high-frequency magnetic fluctuations are found to be modulated by an n = 0 low-frequency mode excited by core sawtooth crashes, revealing a core-edge coupling mechanism. Ar injection also induces the generation of fast electrons (40–100 keV) in the region around ρ ≈ 0.4. These findings have immediate implications for future fusion reactors, as the multiscale physics and core-edge coupling dynamics observed here are directly relevant to the management of alpha particles generated by fusion reactions.