I disagree with your comments. No believer will be lost, because believers are given eternal life based on free grace, and you cannot be given eternal life only to have it be turned into temporary life, because that would contradict Bible.
Notice the key words are, "I NEVER knew you". These people never believed in Jesus in the first place as their Lord and Saviour. They never placed sincere belief in Jesus and were never born again, that's why Jesus says, "I NEVER know you", because if a person genuinely comes to Christ by faith they are KNOWN by Jesus so Jesus could never say, "I NEVER knew you".
These people in Matthew 7:21-23 are all the fake and impostor "believers" who never came to Christ in the first place and only sought to profit from Jesus and didn't do anything for Jesus, but only for themselves and their own profit. I even know a person who tells me that they believe in God, but they have never come to Christ for salvation and invited Jesus into their hearts. It's these types of people that will say to Jesus, "But Lord Lord, didn't I live a good life, I never hurt anyone, I did all these things for you". And others will say, "Lord Lord, I was casting out demons for you". But they were scammers and never born again in the first place.
ONCE a person sincerely comes to Christ by belief and trust, Jesus can NEVER say to that person, "I NEVER knew you".
I think this depends greatly on how we define "believe". Satan believes because he knows. We believe through faith. Believing doesn't require submission, but faith requires belief. But I get what your intention is, because belief from scripture rarely means to simply "believe" in the way that we can believe in Santa Clause or the Tooth Fairy because we are all mature adults and know that one of those doesn't even exist.