Different theologians give different answers to the question, whether salvation can be lost.
But see (Mat. 24:24) “For there will arise false christs, and false prophets, and they will show great signs and wonders, so as to lead astray, if possible, even the chosen ones.”
From this verse it seems that the devil does not know whether it is possible to “lead astray” the “chosen ones”.
It seems for me, that God has deliberately wrote Bible in such way that the devil cannot understand whether salvation can be lost. I think, devil is more clever than us, so we also don’t know the answer to this question.