newby here, dont kill me

so i got muself a coinbase wallet and created an address, and I downloaded Bitcoin core/qt and it's currently syncing

where within the app can i see my wallet address, and is it possible to use any other currency (eth, litecoin, etc) within the bitcoin core?

and finally, what is the actual purpose of bitcoin core, can I buy with it? or is it only receiving BTC first and then sending BTC?