What is the ruling if I recited the final Tashahhud after the first Tashahhud by mistake, while still having the third and fourth rak'ahs remaining: Should I say the tasleem and repeat the prayer, or should I rise for the third rak'ah?

If a worshipper recites the supplications of the last tashahhud (definition) in the wrong place, this action does not invalidate their prayer intentionally, nor does it necessitate the prostration of forgetfulness (sujud (definition) al-sahw). They should complete their prayer, and there is nothing upon them.