Gold can be inflated the same way as any other currency. Since people don't typically trade in physical gold, but in certificates used to represent the gold, it is possible to print more certificates than you have gold. While this is a fraud, it is an increase in the money supply.

Yes, paper gold isn't gold. Or at least it won't be when you need it to be.

Inflation is when the money supply increases in relation to the real wealth that it represents, not when the money supply increases in absolute terms.

Gold's value in fiat currency goes up with the fiat currency's inflation.