Understanding natural groundwater quality patterns, quantifying groundwater pollution and assessing the performance of waste disposal facilities require modeling tools accounting for water flow, transport of heat and dissolved species as well as their complex interactions with solid and gaseous phases. Here we present, CORE2D V4, a COde for modeling partly or fully saturated water flow, heat transport and multicomponent REactive solute transport under both local chemical equilibrium and kinetic conditions. It can handle abiotic reactions including acid-base, aqueous complexation, redox, mineral dissolution/precipitation, gas dissolution/exsolution, ion exchange and sorption reactions (linear Kd, Freundlich and Langmuir isotherms, and surface complexation using constant capacitance, diffuse layer and triple layer models) and microbial processes. Hydraulic parameters may change in time due to mineral precipitation/dissolution reactions. A sequential iterative approach is used for the numerical solution of coupled reactive transport equations. The capabilities of CORE2D V4 are illustrated with six selected applications involving: 1) A laboratory concrete degradation experiment, 2) The long-term geochemical evolution of the near field of a High Level Radioactive Waste (HLW) repository in clay, 3) Cation exchange in a physically and geochemically heterogeneous medium, 4) An experiment of CO2 injection in the vadose zone, 5) The prediction of the water quality of an open pit lake, and 6) Coupled thermo-hydro-chemical processes of compacted bentonite after FEBEX in situ test.