3rd offline tournament

I recently wondered: either I'm not doing something right, or it's already summer. When playing the second-round missions on TE, my monsters don't gain experience (even though it was stated that their leveling up is allowed). When playing on WoG, they do gain experience. And another thing. According to Natasha: "You can also take any troops to the arena (including those obtained using the skeleton transformer), except for skeletons!!!" How is that possible? What can you get using the skeleton transformer besides skeletons? I apologize in advance if the questions are silly.