The high-mass star-forming core G31.41+0.31 is one of the most chemically rich hot molecular cores in the Galaxy. In particular, the first detection outside the Galactic Center of the simplest sugar-like species, glycolaldehyde, has been obtained towards G31, and heavy complex molecules such as methyl formate, ethanol or ethylene glycol have also been observed. The chemical complexity of this core has been studied in detail by our group thanks to observations with multiple telescopes (ALMA, NOEMA, SMA, IRAM 30m, and GBT). In addition, high-angular resolution ALMA observations have allowed us to study the physical structure (temperature and density profiles) and the properties of the rotation and infall of the core. Physical and kinematical properties have been derived from complex organic molecules, including prebiotic species, which have proved to be excellent tracers to study star formation. In this contribution, I will also introduce the unbiased spectral line survey GUAPOS, to be carried out with ALMA covering the full Band 3 at 3mm.