Herein we review novel two-dimensional (2D) glassy-graphene that is in an intermediate state between glassy carbon and graphene and that has high crystallinity but curly lattice planes. A polymer-assisted approach is introduced to grow an ultra-smooth (roughness, <0.7 nm) glassy-graphene thin film at the inch scale. Owing to the advantages inherited by the glassy-graphene thin film from graphene and glassy carbon, the glassy-graphene thin film exhibits conductivity, transparency, and flexibility comparable to those of graphene, as well as glassy carbon-like mechanical and chemical stability. Moreover, an intrinsic bandgap arising from the distorted lattice structure enables glassy-graphene to exhibit comparable or even improved photodetection and chemical sensing capability, compared with pristine gapless graphene. Consequently, high-performance and transparent photodetectors based on $\mathrm{MoS}_{2} /$ glassy-graphene heterostructures with high detectivity were fabricated, exhibiting marked improvement of charge transfer and distinct wavelength selectivity. Meanwhile, the vis-NIR photodetection and chemical sensing device is developed based on glassy-graphene that meets similar property requirements. The signal-to-noise-ratio of the multifunctional device for detecting acetone shows more than $50 \%$ improvement over the device based on graphene. Thereby, large scale 2D glassy-graphene thin film has great potential applications in flexible electronics, photonics and chemical sensing.