Ah ok, you are flying a reach module.
The way i understand to go is do this postprocessing way. Not RTK, but PPK (Post-Processing Kinematic)
The workflow for this is not my area. You might wanna search for @Luke_Wijnberg on this fora find stuff he posted.
1: how i can make sure the rover is fixed with base ?
Maybe here
2: i want to make use of the free correction date form hk website , any suggestions ?
Check what service they provide. VRS? Option to upload data to process or download stream or timespan and Rinex version
3: for the postprocess, if i can get the correction date from somewhere (no matter how i can get , a known point) , i only need one reach(rover) , set it to static mode and log for some periode and then download and work post process,same procedure of doc instruction ,right ? make sure the formate is correct .
Yes