1) are the groove connector 5v or 3v3
2) are the groove connectors connected to the LS/HS or to the micro.
The answer to both of the above questions is "Both, depends on which
connector you use", although since the since the sensor board does not
have a HS connector there's no chance there's anything attached to the HS.
The connectors that run a 3.3v are clearly marked on the board's
silkscreen (four of the baseboard GPIO sockets and the connectors for
I2C1), all others are 5v.
For which connectors are attached to the baseboard and which are
attached to the AVR then its non-trivial to describe... but there's a