According to Fermi-Dirac statistics, the pair correlation function within a superconductor must be antisymmetric, and an odd permutation among spin, parity, orbital index, and time (known as the SPOT criterion) results in a sign reversal of the pairing amplitude. If the crystal structure hosting superconductivity lacks inversion symmetry, parity is not a ‘good’ quantum number, which allows for a mixed-parity superconducting order parameter and, thereby, gives rise to a variety of unusual properties. Here we show, for the first time, the stabilization of a 2D tetragonal superconductor, Nb₃Ge, with a ‘global’ acentric structure of P4mm symmetry, which is composed of nanometer-sized domains with ‘local’ chiral P2 symmetry. We observe various signatures of 2D superconductivity, including a Berezinskii-Kosterlitz-Thouless transition, a Ginzburg-Landau coherence length much larger than the film thickness, and an enhanced in-plane upper critical field beyond the Pauli limit. All these results point to an unconventional Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) type pairing. Remarkably, we also find evidence of a field-free superconducting diode effect (SDE), indicating that the system breaks both inversion and time-reversal symmetry (TRS). We attribute the field-free nature of the SDE to a mixed parity superconducting state resulting from the non-centrosymmetric structure, which further breaks TRS due to the presence of domains of ‘local’ chiral P2 symmetry. These findings highlight the potential of strain engineering in establishing new superconducting states with intrinsic broken TRS, thereby opening up new possibilities for future applications.