No, it is not. You can add multiple commercials for one application. There are two ways to do this. Either show different ads in different places, or use network mediation.
For the first option, you can try interstitial ads, which are mainly full-screen ads and can be displayed on loading screens (this looks good in the game, but you will get poor ratings if it is not in the game application. Personal experience). Or you can also use banners from different networks on different screens of your game.
Now the second option of mediation is considered more convenient and relatively simple and less risky. You select one primary network provider and mediate ads from other network providers through the SDK of the primary advertising provider. The priority of the advertising provider can be set manually in the control panel, although not all providers provide this option. Thus, this was mainly decided by filling speed.
I used Admob mainly for mediation banner ads. It supports a wide range of network providers and non-mediation networks, and you can create custom events. iAd is supported in admob, the rest can be supported using custom events.