1.-Is it possible to change the language or text of the music player?
2.- When adding beat to chart, how can I modify the License options?
3.- How can I change the text of the chart at the main menu(homepage)?
Yes it is possible to change the language. You can visit this blog for more info on how to change language https://translatepress.com/change-wordpress-language/
You can change the license option while adding beats and assign the related files for download according to license. Can you please explain more about the test that you need to change on homepage