Yes, iTel S41 runs on the latest Android 7.0 and thus having support for the multi windows operations.
Yes, iTel S41 does have the fingerprint sensor.
Yes. In fact, iTel S41 has ring indicator which blinks when you get a new notification.
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.
Yes, iTel S41 does have a memory card slot.