Is it permissible to visit the graves of the righteous Awliya (friends of Allah) and ask them for supplication, while believing that Allah is the one who benefits and harms? And is it permissible to visit those who are believed to be among the righteous Awliya of Allah, based on the hadiths regarding the presentation of deeds to the deceased and the presentation of prayers upon the Prophet?

The question encompasses several matters, some of which have been previously answered:

To clarify the permissible and impermissible forms of tawassul (seeking proximity to Allah through an intermediary), whether the deceased can hear the speech of the living, the difference between a wali (saint/friend of Allah) and a pretender, and the difference between tawassul and istighathah (seeking aid/succour), refer to previous fatwas. Going to the graves of the deceased and asking them for supplication is an act of istighathah (seeking aid) from them, and it is considered major shirk (polytheism), even if the intention is to seek their intercession with Allah, because this was the very argument of the polytheists. Visiting graves is permissible for all Muslims, including those referred to as righteous awliya (friends of Allah), provided there is no prohibitory factor, such as the grave being inside a mosque, or practicing polytheistic acts there like supplicating to it, sacrificing for it, or making vows to it. Among the prohibitory factors is traveling solely for the purpose of visiting. The hadith mentioned in the question, which claims to be narrated by Al-Bukhari, is not authentic and was not narrated by Al-Bukhari nor by any of the compilers of the Six Books; in fact, it is not authentically reported from the Prophet (peace be upon him). The ahadith that speak of the deeds of the living being presented to the deceased are not authentically reported from the Prophet (peace be upon him). What is authentic in this regard is that the souls of the believers ask the newly deceased about those they left behind in this world, which indicates that the deceased do not know what the living do after them. It is not permissible to ask for supplication from prophets and righteous people after their death, as that is a means to shirk and worshipping them instead of Allah, unlike asking them during their lifetime. Among the proofs against the permissibility of tawassul through the Prophet (peace be upon him) after his death is the hadith of Umar's tawassul through Al-Abbas (may Allah be pleased with them both) after the Prophet's death. What is narrated about Adam's tawassul through the Prophet (peace be upon him) is weak.