Bosch Sensortec has changed the pinout in the datasheet for the BNO055, it was probably an error in the data sheet:
BST-BNO055-DS000-12 | Revision 1.2 | November 2014:
BST-BNO055-DS000-18 | Revision 1.8 | October 2021:
We connected in our schematic PIN10, Pin15 and PIN16 with GND, could this be a problem? PIN4 (nBOOT_LOAD_PIN) is alwas HIGH.
Yes, the latest datasheet fixed some issues on the recommend pin connection. Please always follow the recomondation from the latest datasheet.
For your issues:
1. pin 10 as debug pin and output to indicator if bootloader mode was entered or not. If sensor enter the bootloader mode, it will driven to high. Since your nBOOT_LOAD_PIN is always high means you didn't enter bootloader mode, it could be no issue for you so far.
2. pin 15 and 16 are now recommended to be DNC. The reason is if you connect them to GND, you will see extra current consumption from sensor. There is no function impact while connect those two pins to GND. But if you care about the system power consumption, you need to change the connection of those two pins to DNC.