Hello and welcome to CC.
You don't need to be "licensed" to teach and preach. You just need to find a street corner.
However, if you want to do so in a church, you must conform to that church's requirements for adequate and appropriate preparation, which may include licensing.
I believe that you will be better prepared to teach and preach if you have worked through the issues, learned the languages, understood church history and bible history, all of which you can learn at seminary (or a good university). The likelihood that you will learn all this on your own is small... but not impossibly so.