Do God's saints know the hidden matters so that they may supplicate for people with what is appropriate for them, or is that a degree of sainthood, and what are the ways to achieve that?

If "knowledge of inner matters" refers to the absolute unseen, then it is something God has kept exclusively to Himself, and He reveals it to none but His messengers. However, if it refers to the relative unseen, then there is no impediment for God to inform some people of it through inspiration, perspicacity (firasah), or truthful dreams.

These matters are not a condition for sainthood (wilayah). Rather, the core of the matter revolves around steadfastness in one's state and its conformity to the Qur'an and Sunnah (definition). For God's saints are "those who believed and were ever God-fearing." The occurrence of miracles (karamat) is not an end in itself. The servant is required to achieve sincerity to God in his actions and to strive for their conformity to the Sacred Law, for by doing so, he attains God's sainthood. Abu Ali Al-Jawzajani said: "Be a seeker of uprightness (istiqamah), not a seeker of miracles (karamah)."