Spacetime singularities arise naturally in General relativity both in black holes and in cosmological evolution. In this article we work within a spherically symmetric modified-gravity framework in which the same field equations admit both regular black hole solutions and a regular cosmological evolution. In both settings we can introduce a regularization scale ℓ that characterizes the regime in which regularization effects become important. We consider observational constraints on ℓ coming from both black holes and cosmological observations: quasinormal-modes, tidal deformability and black-hole shadows, together with the primordial helium abundance, the effective number of neutrino species. In the black hole sector the strongest constraint comes from ringdown measurements that bound ℓ/M ≲ 0.4, corresponding to ℓ ≲ 10^5 m for a representative 100 M⊙ remnant. In the cosmological sector, the strongest constraint comes from primordial helium abundance: ℓ ≲ 10^8 m. The family of models considered here generically predict an upward quasinormal-mode frequency shift, a smaller shadow radius, a lower helium abundance, and a larger effective number of neutrinos, yielding a consistent cross-sector signature of spacetime regularization that can be exploited to break degeneracies with other physical or astrophysical effects.