Gold ultimate subscription

Game pass ultimate includes gold and the game pass subscription so if you have the gold and purchase the ultimate subscription it will cancel the gold subscription and put it in with the ultimate. The Gold subscription will show as being cancelled in your
subscriptions.

When you upgrade to Ultimate, it converts any gold you had on your account to an Ultimate subscription which basically cancels your just gold subscription since Ultimate includes gold. So by cancelling Ultimate you then cancel your gold subscription as
well.

If he has Ultimate it will. If the Ultimate subscription ends and he adds Gold he'll have the full subscription to Gold.

What you bought would have been Game Pass Ultimate, not just Game Pass. Ultimate includes Gold so if you have a standard Gold subscription when you purchase Ultimate, it is converted to Ultimate as well. In order to go back to regular Gold, you would either need to cancel your Ultimate subscription or wait for it to end and then add a regular Gold subscription.

It depends on what you did to try to downgrade. In order to downgrade from Ultimate to just a standard Gold subscription, you would need to cancel Ultimate (or wait for the subscription to run out). Once it has completed ended, then you add a new Gold subscription.

If you tried to downgrade by adding a standard Gold subscription, the Gold would have been converted to Ultimate instead of changing the type of subscription. Then by cancelling Ultimate, you cancelled everything.