Yes, iTel S41 runs on the latest Android 7.0 and thus having support for the multi windows operations.
Yes, you can use 2 different WhatsApp accounts in iTel S41. Not only that, you can use 2 different Facebook, Instagram and Twitter accounts as well.
No. iTel S41 does not gorilla glass but it's display is scratch resistant.
Yes, iTel S41 does have the fingerprint sensor.
Yes, iTel S41 does have VoLTE support.