Is the prayer valid if the worshiper recites the Abrahamic prayer, then the greetings (tahiyyat) in the last tashahhud, then says the taslim (salaam)?

The prayer upon the Prophet, peace and blessings be upon him, is only considered valid if it occurs after the Tashahhud. Whoever performs it before the Tashahhud is required to repeat it after it, otherwise their prayer is nullified according to those who consider it a pillar, which is the preponderant opinion. Whoever recites the Ibrahimiya prayer before the Tashahhud and does not repeat it after it, their prayer is incorrect and they are required to repeat it, except that Shaykh al-Islam Ibn Taymiyyah preponderates against repeating the prayer for one who left a pillar or condition out of ignorance. There is no repetition according to the view of those who do not consider the prayer upon the Prophet, peace and blessings be upon him, a pillar, but repetition is more cautious and absolves one's responsibility.