Q3 Fisrtly not agnologing Jesus as the true Son of God but mearly as an angel, human messenger as well as not accepting or minimising his word as final would have great cause to drift away. Men would have a choice to accept his opinion or not.
By taking care to take heed of his word in the Gospel, and by doing as well as believing it to be true then we would have no reason to drift away "We must pay more careful attention, therefore, to what we have heard, so that we do not drift away."
Jesus describes the "Parable of the Sower" as different circumstances and influences of the enemy and the outside world eg towards the Gospel and whether we choose to believe, understand and use the words of our Lord.