WIFI tethering/hotspot with Mecool KI Pro (frequency, visibility)

General
1

I want to use WIFI tethering on Mecool KI Pro. It works already but I have two issues which I want to change.

  1. How can I change the tethering frequency to use 5 GHz instead of 2.4 GHz?
  2. The wifi network CoreElecHS isn’t found on certain smartphones (Poco X3 Nfc, Poco X4 Pro 5G). What could be the reason for this issue? How can I make it visible for all devices?