They are all different, and do different jobs
Single Replacement- A+BC=AC+B
single-replacement reaction is a type of oxidation-reduction chemical reaction when an element or ion moves out of one compound and into another. That is, one element is replaced by another in a compound.
Double Replacement- AB+CD=AD+CB
Double replacement is a chemical process involving the exchange of bonds between two reacting chemical species.
Combustion- CHO+ O2=CO2+H2O
Combustion is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species.