Private keys are usually not made available to the wallet owner, (although some wallets allow you to import it) rather you are given a seed phrase or recovery phrase.
Not true. You can get private key in almost all of the software wallet (in desktop/PC). If you are using Electrum-
1. Go to address tab.
2. Select any address. Right click the mouse. You will see
Private key option. Click there and get your private key for that address.
If you are using Bitcoin Core client-
1. Go to console.
2. Type [dumpprivkey][your address] & hit enter.
I didn't use Bitcoin Core wallet yet though but that's the basic.
One more info I want to point out-
1 Private Key = 1 particular address
Seed Key = 1 wallet which may include wide variety of addresses.