Using the DFT+dynamical mean-field theory (DFT+DMFT) method we study the normal-state electronic structure, orbital-dependent quasiparticle renormalizations, Fermi surface, and magnetic correlations in the recently discovered alternating single-layer bilayer hybrid Raddlesden-Popper nickelate superconductor La${}_5$Ni${}_3$O${}_{11}$ (1212-LNO). Our results for the $DFT+DMFT$ electronic states exhibit qualitative differences for the structurally distinct single-layer and bilayer Ni ions, implying the importance of confinement and orbital-dependent correlations. The partially occupied Ni $e_g$ electronic states originating from the bilayer Ni ions form strongly renormalized quasiparticle bands with a large enhancement factor $m^{*}/m\sim 3.5$ and 4.2 for the Ni $x^2-y^2$ and $3z^2-r^2$ orbitals, respectively, implying the proximity of the Ni $3d$ states to orbital-dependent localization. Moreover, the $e_g$ states of the single-layer Ni ions exhibit an orbital-selective Mott insulating state, with a narrow energy gap for the Ni $3z^2-r^2$ states and metallic, strongly incoherent (non-Fermi-liquid) Ni $x^2-y^2$ ones. Our analysis of magnetic correlations suggests the formation of intertwined spin and charge density wave stripes in the bilayer NiO${}_6$ slab, in close similarity to the double-layer material. We refine two major instabilities, a leading one is associated with a propagating wave vector ${\bf Q}=(\frac{1}{3},\frac{1}{3})$ ({associated, e.g., with anup-down-0" spin pattern or$d^8$–$d^8$–$d^8\underset{\_}{L}$’’ charge-density wave with Ni $d^8\underset{\_}{L}$ ions bonded in an interlayer spin polaron}), competing with the bicollinear $(\frac{1}{4},\frac{1}{4})$ (``up-up-down-down") stripe state. In contrast, the single-layer Ni $3d$ electrons exhibit instability toward the N'eel-type magnetic state. Under pressure, 1212-LNO undergoes an orbital-selective Mott insulator-to-metal phase transition, associated with metallization of the single-layer Ni $e_g$ states. As a result, the single-layer Ni $e_g$ bands exhibit non-Fermi-liquid (bad metal) behavior with strongly incoherent spectral weights near the Fermi level. We note that correlation effects result in a remarkable reconstruction of the symmetry and strength of magnetic correlations as compared to that obtained within DFT. In fact, we observe a crossover from single-layer (as obtained within DFT) to double-layer dominated magnetic correlations.