Siman 481
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א אַחַר אַרְבַּע כּוֹסוֹת אֵינוֹ רַשַּׁאי לִשְׁתּוֹת יַיִן, אֶלָּא מַיִם. הַגָּה: וְכָל הַמַּשְׁקִין דִּינָן כְּיַיִן (בֵּית יוֹסֵף). וּמִי שֶׁהוּא אִיסְטְנִיס אוֹ תָּאֵב הַרְבֵּה לִשְׁתּוֹת, יָכוֹל לִשְׁתּוֹת כּוֹס חֲמִישִׁי וְיֹאמַר עָלָיו הַלֵּל הַגָּדוֹל. (מָרְדְּכַי).
1 Not to drink after the 4 cups. Containing 2 paragraphs: After the four cups, he is not allowed to drink wine, but rather water. Rema: And the law of all drinks (besides water) is like [the law concerning] wine (Beit Yosef). And one who is delicate or greatly desires to drink may drink a fifth cup [of wine] and say the Great Hallel upon it (Mordekhai).
ב חַיָּב אָדָם לַעֲסֹק בְּהִלְכוֹת הַפֶּסַח וּבִיצִיאַת מִצְרַיִם, וּלְסַפֵּר בַּנִּסִים וּבַנִּפְלָאוֹת שֶׁעָשָׂה הַקָּדוֹשׁ בָּרוּךְ הוּא לַאֲבוֹתֵינוּ, עַד שֶׁתַּחְטְפֶנּוּ שֵׁנָה. הַגָּה: וְכָל דִּין לֵיל רִאשׁוֹן יֵשׁ גַּם כֵּן בְּלֵיל שֵׁנִי (אָגוּר). וְנוֹהֲגִים שֶׁלֹּא לִקְרוֹת עַל מִטָּתוֹ רַק פָּרָשַׁת שְׁמַע, וְלֹא שְׁאָר דְּבָרִים שֶׁקּוֹרִין בִּשְׁאָר לֵילוֹת כְּדֵי לְהָגֵן, כִּי לֵיל שִׁמּוּרִים הוּא מִן הַמַּזִּיקִין.
2 A person is obligated to engage in the laws of Passover and the story of the Exodus from Egypt, and to recount the miracles and wonders that the Holy One, Blessed be He, performed for our ancestors until sleep overtakes him. Rema: And all the laws of the first night also apply to the second night (Agur). It is customary to recite only the Shema before going to sleep and not the other passages that are usually recited on other nights, in order to provide protection, as this is a ‘night of watching’ from harmful forces.