Two of the most promising routes for catalytic polyolefin upcycling are hydrogenolysis and hydrocracking. They require no additional feedstocks as metathesis or alkylation, and are less susceptible to deactivation than pyrolysis or Haag-Dessau cracking on monofunctional acidic catalysts. Besides, these two reactions have been crucial parts of the oil refining industry and thus extensively studied with small alkane substrates, with established operation infrastructure and fundamental understanding partially applicable to polyolefin substrates. Both hydrogenolysis and hydrocracking refer to C-C bond cleavage under H2 on supported metal catalysts, but the former cleaves C-C bonds on the metal, while the latter cleaves C-C bonds (and isomerizes substrates) on Brønsted acid sites after dehydrogenation on the metal, thus requiring metal-acid bifunctional catalysts. Despite initial success, the catalyst development for both routes is at a very preliminary stage. Meanwhile, polyolefins substrates often behave very differently from small alkanes, and fundamental understanding specific to them is lacking. For hydrogenolysis, most studies used catalysts with high noble metal (Ru or Pt) content, and the selectivity needs to be steered away from low-valued gas alkanes, especially CH4, to high-valued liquid alkanes. We have shown that disordered Ru clusters have better activity and selectivity in the reaction than rigid particles, but the structure-function relationship needs further understanding for the rational design of active sites. For hydrocracking, most studies used expensive, scarce Pt as the metal, and zeolites as the acidic support, the microporous structure of which creates difficulty for the diffusion of long-chain polymers and thus limits active site accessibility. Also, mechanistic understanding is very rare, which hinders tuning product distribution rationally. Furthermore, there are no studies of the two reactions occurring simultaneously, which is common on bifunctional catalysts with small alkanes. This type of studies do not only help understand the complex reaction network, also offer insights on how to choose between the processes and design catalyst functionality.