To address the issues of pose coupling and power system redundancy in conventional multirotor aircraft, this paper integrates the structural advantage of reduced rotor count in bicopters with the pose decoupling advantage of tilt rotors, and proposes a Tiltable Bicopter with Two-degrees-of-freedom Arms (TBTA). First, quaternion-based dynamic and kinematic modeling is performed, and a decoupling control allocation method is investigated based on this modeling. Aiming at the challenges of strong coupling, nonlinearity, parameter perturbations, and external disturbances during its pose transformation process, a Non-singular Terminal Sliding Mode Active Disturbance Rejection Controller (NTSMC-ADRC) for position and attitude control is designed. Simulations verify that the NTSMC-ADRC controller exhibits excellent robustness and disturbance rejection capabilities. Finally, attitude transformation and inclined-surface flight experiments demonstrate its application value for takeoff and landing in non-horizontal plane scenarios, such as slopes, tree environments, and high-rise building areas.