Asking for Unlock Codes on Different Devices?

Hello. My unlock codes are different on my iPhone, iPad and iMac and there have been occasions where I get a warning stating that "some features will not be available" if you do not follow the prompts. last night on my Iphone I received this message, I enter my apple ID & Password, then it asks for the unlock code for my Iphone, then asked me for the unlock code for my Ipad. is this normal? whey Do I need to enter a unlock code for my Ipad in my Iphone?

My Imac asked for this information over a year ago and I never gave it up, this prompt only came after I received a message that a devices has been added to my account, and I did not add a device to my account last night. I was a little worried about security at this point and changed my apple id password. Please let me know this is normal apple operation and I should not worry. Thank you for your time.