Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32L15xxE/Flash/OBR#0x0
Option byte register
Read protection
BOR_LEV
IWDG_SW
nRTS_STOP
nRST_STDBY
Boot From Bank 2
https://github.com/cmsis-svd/cmsis-svd-data