Why did go Pharaoh go each morning to the Nile?
Rashi: Pharaoh made out to be a god who did not need to relieve himself; so he would go early in the morning (before anybody was around) to do so.
Ramban (8:15) and Rashbam: He went for a morning stroll, as is the way of kings.
Targum Yonasan: He would go there regularly to practice witchcraft.
Why, for Makos Dam, Arov and Arbeh, did Hashem instruct Moshe to go and meet Pharaoh when he went to down to the Nile?
Ramban (later) 1 : For Makas Dam, because it was the first Makah, and Hashem wanted Moshe to confront him fearlessly as he made his way there in a show of strength. 2 And for Arov and Barad, which caused widespread death, he wanted to warn Pharaoh in front of the many people (who customarily would accompany the king on his stroll), to give them the opportunity to prevail upon Pharaoh to submit to Moshe's demands.
Da'as Zekenim, Hadar Zekenim (26): These were new warnings, i.e. they were not preceded by a Makah about which he was warned.
For how long may the Lachmei Todah be eaten?
Rashi: For one day and a night, like the meat of the Korban.
Seeing as the Torah permits eating the Korban Todah until the morning, why did the Chachamim curtail the time-limit until midnight?
Rashi (Brachos 9a): In order to distance people from sinning. 1
Rashba (9a): I.e. lest one think that it is still night, and really dawn came, and he will eat and transgress Nosar. See Torah Temimah.
Rashi writes that the Chagigah of Erev Pesach is eaten for one day and a night. He himself explained (Devarim 16:4) that it is eaten for two days and a night!
Ramban, Riva, Moshav Zekenim: There, Rashi explains like Chachamim and Toras Kohanim. Here he explains like Ben Teima. 1 Rashi in Pesachim (96b) brought two Perushim of 'Shelamim that come due to Pesach 2 ' - (a) Temuras Pesach or Mosar Pesach (it was leftover, e.g. it was lost and the owner brought another animal for Pesach); (b) the Chagigah of Erev Pesach.