How are link-check mode and ADR related?

[MarcusWichelmann]

I'm a bit new to LoRaWAN and have seen two methods in the documentation where I'm not very sure about, how they relate to each other: LMIC_setLinkCheckMode and LMIC_setAdrMode.
Maybe you could help me with this.

Here are my questions:

1. When link-check mode is enabled, the library will send regular ADR-requests right? Does this only work, if AdrMode is also enabled, which means, that I must not enable LinkCheckMode without also enabling AdrMode?
2. Do I have to regulary call some method to make LinkCheckMode working? The documentation says the LMIC_setLinkCheckMode method "must be called only if a session is established". Why is that?
3. Should AdrMode and LinkCheckMode be both disabled, before setting the data rate and transmit power manually using LMIC_setDrTxpow? Or is it sufficient to disable AdrMode to make sure my changes don't get overwritten?
4. The documentation states, that ADR "should be turned off if the device is mobile". Does the same apply to LinkCheckMode, too?

Maybe one could clarify this a bit. Thank you very much!