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1. Pages 0-3 (for low- and medium-density devices), or pages 0-1 (for high-density and connectivity line devices) are automatically write-protected.
2. Нет. Разве что через ваш же код через сторонний канал, если в нем баг

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When booting from the embedded SRAM, Flash memory accesses through the code and through data read using DMA1 and DMA2 are not allowed.
The rest of the memory can be programmed by the code executed from the main Flash memory (for IAP, constant storage, etc.), but it is protected against write/erase (but not against mass erase) in debug mode or when booting from the embedded SRAM.