HMC6352 Query&Continuous Modes

Hi, I read the datasheet and don't really understand this two modes.

Query mode:

page 8 says " Send 43(hex)slave address to read data and clock out the two register data bytes for heading .An initial "A" command is needed to update the heading after each read."

But page 6 says" After each read command , the HMC6352 automatically performs another get data routine and updates the data registers.This mode is designed to get data on demand without repeating "A" command."!! So do I need to set A command every time I want to read a new data or not?? In my mind, read command is 0x43 ,the slave address. command A is "get data".

Continuous mode: It say that the max measurement rate is 20 HZ, does it means it is really slow,but continuously &automatically update data? But the code in the loop is so fast that runs probably 100 times and the data doesn't change at all,right?