Hi @Petjepet. Select the appropriate board from Arduino IDE's Tools > Board > esp8266 menu and then try compiling the sketch once again. Hopefully it will work as expected after that.
Arduino IDE remembers the board you had selected previously. This can cause the "platform not installed" error in cases where you have made certain changes to the installation of the boards platform for that specific board since the last time you tried compiling. In this case, the solution is to simply select the board again, which will update the configuration of Arduino IDE from the outdated one to the configuration appropriate for the current boards platform installation.
Definitely. The fact that the compilation progressed far enough to get to those library errors proves that you have solved the problem of the "zombie" board selection. So this is progress at least!
Since it is unrelated to the original subject of this topic, please open a new forum topic to request assistance with the library errors. This will ensure it gets the attention of the forum helpers knowledgeable about the subject of your new problem. Make sure to include the full and exact text of the new errors in your post.
You are welcome. I'm glad if I was able to be of assistance.