Salah is not accepted from anyone other than a Muslim.

Qur'an 3:85 (Interpretation of the Meaning)
And whoever desires other than Islam as religion - never will it be accepted from him, and he, in the Hereafter, will be among the losers.

Sanity is considered a key part of legal capacity and is important for a person to be able to perform religious duties and be subject to criminal law. Therefore, a mentally challenged person will not be held accountable for their deeds, and they are not obligated to perform Salah.

A Muslim must be at least the age of puberty before their Salah can be accepted. Puberty is defined by natural, manifest signs, some of which are common to both genders, while others are exclusive to one gender.
Common puberty signs:

• The discharge of sexual fluid (semen), either during sleep or when sexually aroused while awake.
• The appearance of pubic hair, which is different from the soft fuzz that appears before reaching puberty.

Specific signs for females:

• Menstruation: This is the primary sign of female puberty and indicates the age when a girl can become pregnant.
• The appearance of pubic hair, which should be removed by shaving, unlike the fuzz that appears before puberty.
The signs mentioned above indicate puberty. Otherwise, puberty is considered to occur by age. According to Shafi and Hanbali scholars, as well as Abu Yusuf and Muhammad ebin al-Hassan from the Hanafi school, the age of puberty for both males and females is considered to be 15 lunar years.

When performing Salah (prayer), both men and women must observe proper dress to maintain modesty and fulfill the requirements of prayer. This is known as "satr al-‘awrah"—covering the parts of the body that must be concealed during prayer. Clothing should be:

• Clothing must be loose-fitting and not transparent
• Must be clean and free from impurities (najasa)
• Should not be tight or shaped in a way that reveals the form of the body

Dress For Men:
Minimum requirement:

• The area between the navel and the knees must be covered. This is the absolute minimum required for the validity of prayer.
• Covering the shoulders is generally recommended, though not obligatory:

  The Messenger of Allah ﷺ said: None of you must pray in a single garment of which no part comes over his shoulders. Muslim 516

Dress For Women:
Minimum requirement:
The entire body must be covered except for the face and the hands (up to the wrists).

Muslims are required to perform Salah in places that are free from Najasah (impurity or uncleanliness). This means that the ground, prayer mat, and surrounding area should be clean from impurities. A Muslim must perform Wudu (ablution) before praying, unless they have just performed Ghusl (ritual washing). For details, refer to the Wudu page in previous menu..

Facing the direction of the Kaaba (the Qibla) is an essential condition for the validity of a Muslim's prayer. Without facing the Qibla, the prayer is not accepted. This is a fundamental requirement in Islamic worship. If it is not possible to determine the Qibla (the direction of the Kaaba in Makkah), then a person may pray in any direction. Islamic jurisprudence allows flexibility in such cases.

The intention should only be in your mind about what prayer you are about to perform.

Shaykh Al-Islam ebin Taymiyah was asked about the intention when starting an act of worship, such as praying. Is it necessary to utter it verbally, such as saying, “I intend to pray, I intend to fast”? He replied:
“The intention for acts like Wudu, Ghusl, Tayammum, praying, fasting, paying Zakah, offering expiation, and other acts of worship does not need to be uttered verbally, according to the consensus of the Imams of Islam. Rather, the place of intention is the heart, according to the consensus among them. If a person accidentally utters something that contradicts what is in their heart, what counts is the intention in the heart, not what was said.”