Can we find out who has developed the app by looking on the signature?
Yes it's possible, you can check by unzipping the APK, finding the META-INF/CERT.RSA file which contains the developer's public key and using the command openssl pkcs7 -in /path/to/extracted/apk/META-INF/CERT.RSA -inform DER -print. 

For more info have a look at the first section of this link: https://www.evilsocket.net/2017/04/27/Android-Applications-Reversing-101/.