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 the eye protection mode which reduces strain for long reading.
Yes, iTel S41 does have the fingerprint sensor.
Yes. In fact, iTel S41 has ring indicator which blinks when you get a new notification.