If Satan can "spoil" (not sure if that's the proper term) God's plan in one area, such as when he messed up the plan for this earth; then surely he can upset (disturb, hinder, retard?) His plans in other areas. It was not God's plan for sin to enter the universe, or our world, but it happened. It was His plan that all of mankind be saved, but it isn't going to be that way. It was also His plan that Israel be alight to the world, but they failed. None of these things caught God unprepared, of course, since He is omniscient. Being omniscient and omnipotent He is always able to overrule Satan's devices so that good will come out of it. It may be that Stephen was God's first choice, but the end result of his martyrdom did not handicap God or the church. It resulted in the gospel going to the Gentiles much quicker than it would have gone.I'm not convinced that the volume of written material either about him or by him, necessarily qualifies Paul as the 12th apostle. Most of the apostles did not leave us any written material, but they were still apostles.