What is the benefit and value of a human being if abstaining from every sin occurs by Allah's command, and what is the reward for abstaining from sin if it is due to the grace of answered prayers and not by the servant's effort? And should one supplicate to Allah to distance every sin, or only those that are difficult to abstain from?

Supplication is one of the means that a servant is commanded to adopt for the betterment of their condition. Asking Allah for guidance and steadfastness is among the greatest objectives. A servant's supplication that Allah keep them away from sins does not contradict their being rewarded for avoiding them by their own will, choice, and ability. For Allah is the Granter of success for the actions of His servants, and He is the One who rewards for them.