The disadvantage of a single-platform application from the options you provided is:
Exposure of the application is limited.
Single-platform applications are limited to users who have access to that specific platform, which can restrict their reach and the potential user base. The other options address aspects that are less likely to be inherent disadvantages of being single-platform. For instance, while performance optimization can be a concern, single-platform apps can actually be highly optimized for their specific environment. Compatibility issues are also less relevant since a single-platform application is designed to work within one specific ecosystem.