  Since the chemical abundances of stars are the fossil records of the physical
conditions in galaxies, they provide the key information for recovering the
assembly history of galaxies. In this work, we explore the
chemo-chrono-kinematics of accreted and in-situ stars, by analyzing six M31/MW
analogues from the HESTIA suite of cosmological hydrodynamics zoom-in
simulations of the Local Group. We found that the merger debris are chemically
distinct from the survived dwarf galaxies. The mergers debris have abundances
expected for stars originating from dwarfs that had their star formation
activity quenched at early times. Accreted stellar haloes, including individual
debris, reveal abundance gradients in the ELz, where the most metal-rich stars
have formed in the inner parts of the disrupted systems before the merger and
mainly contribute to the central regions of the hosts. Therefore, we suggest
that abundance measurements in the inner MW will allow constraining better the
parameters of building blocks of the MW stellar halo. The MDFs of the
individual debris show several peaks and the majority of debris have lower
metallicity than the in-situ stars for Lz>0, while non-rotating and retrograde
accreted stars are similar to the in-situ. Prograde accreted stars show a
prominent knee in the [Fe/H]-[Mg/Fe] plane while the retrograde stars typically
deposit to a high-[Mg/Fe] sequence. We found that the metal-poor stars
([Fe/H]<-1) of the HESTIA galaxies exhibit between zero to 80 km/s net rotation
which is consistent with the Aurora population. At higher metallicities, we
detect a sharp transition (spin-up) from the turbulent phase to a disk-like
rotation. Mergers debris are similar in the [Fe/H]-[Mg/Fe] plane. However,
combining a set of abundances allows to capture chemical patterns corresponding
to different debris, which are the most prominent as a function of stellar age.
