LHG

I’m looking to book round trip flights on the Lufthansa website from Lax-Fra-Vfa and Vfa-Jnb-Fra-Lax all on one PNR.

The Lax-Fra is a LH flight and the Fra-Vfa is a Eurowings Discover codeshare flight. When checking in for the Lax-Fra flight will LH also issue my boarding pass and transfer my luggage for the next flight on EW Discover from Fra-Vfa?

On the return leg when checking in for the flight from Vfa-Jnb an Airlink flight do I check in with Airlink or LH? If Airlink do I use the same PNR# issued by LH or do I need the Airlink PNR#?
Will Airlink also issue my boarding passes for the LH flights Jnb-Fra and Fra-Lax and transfer my luggage to the Jnb-Fra flight from Vfa? If Airlink only transfers my luggage does LH have a airside transfer counter at Jnb to pickup my boarding passes for the Jnb-Fra-Lax flights?

I know that LH and Airlink are Star Alliance members, have an interline agreement and both use Amadeus Altéa Passenger Services System.