An analytic operator solution of a generalized quantum mechanical Hamiltonian of two-mode Bose-Einstein condensates (BECs) is obtained for short-time dynamics and the same is used to investigate the nonclassical properties of the modes present in the system. Nonclassical characters are observed by means of single-mode and intermodal quadrature squeezing, single-mode and intermodal sub-Poissonian boson statistics, and intermodal entanglement. In addition to the traditionally studied lower-order nonclassical properties, signatures of higher-order nonclassical characters of two-mode BEC systems are also obtained by investigating the possibility of higher-order antibunching and higher-order entanglement. The mutual relation among the observed nonclassicalities and their evolution (variation) with time and the ratio of the single boson tunneling amplitude ($\ensuremath{\varepsilon}$) and the coupling constant for the intramodal interaction ($\ensuremath{\kappa}$) are also reported.