What does the mujtahid's deserving of reward indicate, whether he is correct or mistaken, and is the ruler's ijtihad on an issue sufficient to preclude the renewal of ijtihad on similar issues, and why?

This hadith indicates that the mujtahid is rewarded, whether he is correct or mistaken, and that every mujtahid is rewarded if he exerts his utmost effort, and not every mujtahid is correct. The mujtahid must renew his consideration of issues and emergent matters, and not rely solely on what preceded him, as it is possible for something to appear to him that had not appeared before.