Q.deadheading petunias
If I just pull the dead flower off, will that make the plant create a seed pod, which is what I want to do on some of the plants so I have seeds? I rarely get a seed pod, so if I pull the flower off rather than cutting the whole thing off, it will not create a new flower in that exact place, correct?

When you deadhead a petunia you encourage more blooms and discourage the formation of seed pods. If you stop deadheading the petunias, the seed pods will form naturally. When the bloom fades and dies, the seed pod will begin to develop.
For more information on deadheading petunias, please visit the following link:
https://www.gardeningknowhow.com/ornamental/flowers/petunia/deadheading-petunias.htm