Does a Muslim attain the virtue of every good deed if he intends the general virtue and does not intend the specific virtue for each detail, or is it a condition to account for each virtue separately? What about someone who is ignorant of the virtues of deeds? And does the intention that the work is for the sake of Allah substitute for accounting when one forgets?

A Muslim is rewarded for his intention. So, if he intends to perform an act of obedience to Allah and is keen on its reward, then becomes ignorant of its virtues or forgets the intention, he will still receive the full reward for it. Ibn Taymiyyah mentioned that whoever intends good, and does what he is capable of, but is then unable to complete it, will receive the reward of one who completed it. He cited as evidence the hadith: "Indeed, there are men in Medina who, no journey you undertook nor valley you crossed, but they were with you, detained by an excuse." And also the hadith: "If a servant falls ill or travels, what he used to do when healthy and at home will be written for him." As long as a Muslim is keen on the reward of an act of obedience and intends it for the sake of Allah, he will receive all its reward, by the grace and mercy of Allah.