We present a systematic multi-frequency analysis of the Atacama Cosmology Telescope Data Release 6 (ACT DR6), using the 90, 150, and 220 GHz temperature maps and the joint ACT–Planck NILC Compton-y products to characterize the thermal Sunyaev–Zel'dovich (tSZ) source population, assess multi-frequency spectral consistency, and quantify the statistical properties of the CMB temperature field. A blind search of the NILC Compton-y map yields 200 tSZ candidates above 5 sigma, with the brightest at 51.2 sigma and a confirmed recovery of the Bullet Cluster (1E 0657-56) at 3.4 arcmin separation. Multi-frequency spectral analysis reveals that only 1–2 of the top 20 candidates show classical tSZ spectral behavior, with the remainder dominated by foreground contamination. We report a compact source at (RA, Dec) = (291.2, -29.2) deg with amplitude 758 muK, spectral index alpha approximately -0.4 consistent with synchrotron emission, and 41 sigma Compton-y significance, whose physical nature requires multi-wavelength follow-up to determine. The f150 temperature field exhibits excess kurtosis kappa approximately 47 (more than 100 sigma above Gaussian simulations), attributable to unresolved extragalactic sources. We measure a hemispherical power ratio of 0.93 +/- 0.07, consistent with isotropy, and identify four sky regions with anomalously low cross-frequency correlation (rho less than 0.12). Radial profile analysis flags five clusters with anomalous morphologies (z-score greater than 2): two with extreme concentration and three with extended profiles indicative of mergers. Cross-frequency coherence measurements establish pair-specific scale cuts from ell_max ~ 1000 (220 GHz pairs) to ell_max ~ 1500 (same-band pairs). Null tests confirm internal consistency: split-map agreement, cosmic birefringence |beta| less than 0.01 deg, and isocurvature limits TB, EB less than 1 sigma. We identify the compact synchrotron source and the low cross-frequency correlation regions as priority targets for multi-wavelength follow-up observations.