Can the dwellings face different streets on a corner block?

Yes, potentially. The ACT Missing Middle Housing Design Guide specifically shows dual occupancy developments on corner blocks, including attached and detached layouts that make use of the different street frontages.

Whether each dwelling can face a different street will depend on the particular block and design, including how the development addresses the street frontages, parking access and surrounding streetscape.

Reference: ACT Missing Middle Housing Design Guide – Part 3, Section 3.1B Multi-occupancy - https://www.planning.act.gov.au/__data/assets/pdf_file/0020/3092411/ACT-Missing-Middle-Housing-Design-Guide.pdf?utm_source