1) pin 10 in the lastest datasheet of BNO055 was clearly indicated as Bootloader indicator pin and recommend to be DNC. it is one output debug pin and will be driving to high when you enter special bootloader mode. So, in your design, leave to NC has no any problem.
2) We didn't met such issue before. From the given procedure, i didn't found any abnormal. If sensor set reset during reading data phase all the time, i suggest you to check the VDD / VDDIO line during sensor working first. In general, there are 3 ways to reset BNO055
a. soft reset by set RST_SYS bit into SYS_TRIGGER register
b. Use the reset pin to reset sensor
c. POR (power on reset)
For normal data streaming stage, sensor should working continuously without reset. Since you didn't set reset command and didn't trigger reset pin, the only suspection now is the VDD / VDDIO line.
... View more