Here we present 3D confined assembly of polystyrene-b-polyisoprene-b-poly(2-vinylpyridine) (PS-b-PI-b-P2VP) ABC triblock copolymers into particles with tunable shape and internal structures. Under weak confinement (i.e., ratio of the particle size to the periodicity dimension of the block copolymer D/L-0 > 4), surfactants in the suspension show significant influence on the morphology of the particles. Unique structures, such as onion-, bud-, and pupa-like particles, can be obtained by tailoring properties of the surfactants. Both particle shape and internal structure can be reversibly tuned through pathway independent solvent vapor absorption annealing. While under strong confinement (e.g., D/L-0 < 2), commensurability between D and L-0 will dominate the structure of the particles. Moreover, these structured particles with cross-linkable PI domain can be selectively cross-linked and disassembled into isolated nano-objects. Janus nanodiscs with PS and P2VP chains at different sides can be obtained from pupa-like particles. Such nanodiscs can act as surfactants to stabilize oil/water emulsion droplets. This strategy, combining 3D confinement, selective cross-linking, and disassembly, is believed to be a promising approach for constructing structured particles and unique nano-objects.