This Halacha is an excerpt from our Sefer
Buy me here or on Amazon.com
It is permitted to eat Chametz up until the start of the 5th hour of the day on Erev Pesach. Past this time, it is forbidden to eat Chametz. [Practically, this time is equivalent to the time of Sof Zman Tefilah for Shacharis. One is to verify the time on a Zmanim calendar based on his location. One must to be careful to eat only Kosher for Pesach products starting from this time.] See Chapter 2 Halacha 3B for the full details of this matter!
Kashering: Initially, one is to finish any last-minute Koshering prior to the 5th hour of the day [i.e. Sof Zman Achilas Chametz]. See Chapter 9 Halacha 10B!
At what time must Ashkenazim stop eating Matzah Ashira [egg Matzah]?
It is forbidden to eat Matzah Ashira starting from the time that it is forbidden to eat Chametz. Some Poskim rule that even according to Ashkenazim one may eat Matzah Ashira [egg Matzah] until midday. However, practically the custom is to avoid eating Matzah Ashira beginning from the time that one must stop eating Chametz, which is from the beginning of the 5th hour.
From what time are those who are accustomed to not eat processed foods to begin their stringency?
One is to avoid eating these foods starting from Sof Zman Achilas Chametz, which is from the 5th hour of the day. However, many are lenient to eat processed foods up until the night of Pesach. See Chapter 7 Halacha 5A for further details on this matter!
From what time are those that are accustomed to not eat spices or unpeeled foods to begin their stringency?
One is to avoid eating these foods starting from Sof Zman Achilas Chametz, which is from the 5th hour of the day. However, many are lenient to eat these foods up until the night of Pesach. See Chapter 7 Halacha 7 in Q&A for further details on this matter!
Brushing and Koshering one’s teeth:
Prior to the arrival of the 5th hour, one is to clean and wash his teeth with water to make sure that no crumb of Chametz has remained. If one has fillings, he is to wash his mouth with the hottest temperature of water, from a Keli Sheiyni, that he can intake. It is best to not eat hot Chametz 24 hours prior to doing so. Dentures are to be removed, cleaned and Kashered. See Chapter 9 Halacha 9O for the full details of this matter!
 Implication of Admur 471:6
 Noda Beyehuda 21 brought in Kaf Hachaim 443/7
 Piskeiy Teshuvos 444:3 [He makes no mention of the opinion of the Noda Beyehuda ibid]