The Diels-Alder (DA) pericyclic chemistry is one of the most powerful reactions in synthetic chemistry. We have recently shown that the unique zero-band-gap electronic structure of graphene at the Dirac point facilitates the band-gap-dependent DA reaction of graphene, although graphene is the thermochemical reference for carbon. We have shown that in the DA reactions, graphene can function either as a diene or a dienophile (dual nature). Such DA functionalization of graphene when applied to graphene-FET devices allows balanced functionalization (creation of a pair of new sp3 centers or divacancies) at both A and B graphene sublattices, allowing the fabrication of high mobility DA-functionalized single-layer graphene devices (DA-SLG) with acceptable on/off ratio. The chemistry is thermally reversible via retro-DA chemistry, thus allowing reversible engineering of graphene devices.