TinyRTK with Holybro Pixhawk 4

I have Holybro Pixhawk 4 and a TinyRTK with Tallysman TW3742 antenna.
For now, the RTK feed is coming from NTRIP via internet.
I wonder how I should connect TinyRTK to the Pixhawk, considering I want to use a single telemtry radio with injection.
I understand I need to connect the solderbridge on TinyRTK.
Two main questions :

  1. I guess I have to continue using the original GPS antenna that provides LED, button and compass, right ?
  2. does that mean I have to connect TinyRTK to UART/i2c port 12 ? Will Pixhawk automatically pass the RTCM feed to UART port and into the TinyRTK ?
    Many thanks, Peter