Should the worshiper raise his hands while sitting after the Tashahhud in the second Rak'ah and then stand up and say "Allahu Akbar," or should he stand up first and then raise his hands and say "Allahu Akbar"?

The legitimacy of raising the hands when standing for the third rak'ah is established by the hadith of Ibn 'Umar (may Allah be pleased with them both). Al-Bukhari narrated that Ibn 'Umar used to raise his hands when he stood up from the two rak'ahs, and he attributed this action to the Prophet (peace be upon him). The raising of the hands occurs when standing, not while sitting before rising. This is the madhhab of the Shafi'is.