Not saying “This is for Pesach”-Setting aside products for Yom Tov rather than for Pesach:
Animals: It is forbidden or one to say regarding (his animal) that “this meat is for Pesach.” It goes without saying that one may not say this regarding a goat or sheep. One is not to say this statement on any species of animal, whether wild or domestic, or poultry, whether alive or slaughtered. Rather one is to say “This meat is for Yom Tov.”
Pieces of meat/poultry: One is not to say even regarding meat or poultry, that “This meat is for Pesach”. Rather one is to say “This meat is for Yom Tov”. One is likewise not to say to a messenger “Take this money and buy me with it this meat for Pesach” but rather he is to say “Buy me this meat for Yom Tov.” [This prohibition against saying “for Pesach” applies in any language. This prohibition applies even if one does not own the meat.]
Other items: It is permitted to say “This is for Pesach” regarding fish and all other foods that are not a species of meat at all. However there are Poskim who are stringent to avoid saying this statement on any item, with exception to kernels and the like of things which need to be guarded from becoming Chametz. Practically, it is proper to suspect for their opinion and avoid saying the above statement of “This is for Pesach” regarding any item other than kernels and the like.
Bedieved: If one said the above statement “This is for Pesach” on food, or other item, the food/item nevertheless remains permitted to be eaten/used. This applies, even if one said on a live goat or sheep “This meat is for Pesach”, nevertheless, it is permitted to be eaten. This applies even if it was said on Erev Pesach after Chatzos/midday. (However, some Poskim are stringent and rule that if one said “This is for Pesach” regarding a goat or sheep, then it becomes forbidden to eat forever, whether on Pesach, before Pesach or after Pesach. This stringency applies even if one said the statement on pieces of sheep/goat meat [and certainly if one said it on a live animal]. Practically, it is proper to suspect for their opinion and prohibit the consumption of this goat/sheep meat unless it involves a case of great loss or time of need. One may however in all cases benefit from the meat [such as to sell the meat]. In a case of great loss or great need, one may even be lenient to eat it. The above stringency only applies if the sheep/goat belongs to oneself, or one shares partial ownership over it. If however one does have any ownership of the meat then one is not to be stringent at all against eating it [and the meat may be eaten by its owner].)
One is not to say regarding meat or poultry, that “This meat is for Pesach” or “Buy me this meat for Pesach”. Rather one is to say “This meat is for Yom Tov” or “Buy me this meat for Yom Tov”. This statement is especially forbidden to be said regarding a live animal, and particularly against a goat or sheep. It is proper to avoid saying the above statement of “This is for Pesach” regarding any item, even fish and non-meat products.
Bedieved: If one said the above statements on food, or other items, they nevertheless remain permitted to be eaten. However, if one said this regarding a sheep, whether alive or pieces of meat, then one is to completely avoid eating the meat, even after Pesach. One may however sell the meat, and in a case of great loss or great need, one may even be lenient to eat it. If the sheep or meat does not belong to oneself, his statement is meaningless and the meat may be eaten by its owner.
What is the law of one asked his wife to buy lamb chops for Pesach?
Seemingly, according to all the meat may still be eaten, as the statement was not made at the time of ownership.
What is the law if after buying the lamb chops one said this lamb meat is for Pesach?
If this was said by the father of the house, then one is not to eat it even after Pesach, unless there involves a great need or great loss. One may give or sell the meat to others. If the statement was said by other family members, the meat remains permitted to be eaten.
May one say “This meat is for Pesach Sheiyni”?
One is to avoid doing so.
 469/1-2; Michaber 469/1; Pesachim 53b
 Admur 469/1; Michaber ibid; Pesachim ibid
 Admur 469/1; Levush 469; Rosh on Pesachim ibid
The reason: This prohibition is due to Maaras Ayin, as the listener may think that one is sanctifying the animal/meat as the Pesach sacrifice, and thus later when he eats it, people will think he is eating Kodshim outside of the Temple. [Admur ibid; Michaber ibid; Pesachim ibid]
 Admur ibid; Maharil brought in M”A 469/1; M”A ibid concludes that regarding chicken this is a mere stringency, as the letter of the law prohibition only applies to animals that can be offered to the Mizbeiach.
The reason: As chicken requires slaughtering and is thus similar to other meat. [M”A ibid; Taz 469/2]
 Admur ibid; Michaber ibid regarding any animal;
 Admur 469/1; Michaber ibid
 The reason: As if he says this meat is for Pesach the observer may think one is sanctifying the meat as money to purchase the Pesach sacrifice, meaning that he will sell the meat and purchase the Pesach sacrifice with its worth. Now, later on when he eats this meat it will appear to the observer that he is doing Meila to Kodshim. [ibid]
 Admur ibid; Peri Chadash 469; Yerushalmi Pesachim 7/1
 M”B 469/5
 So is implied from Admur ibid
 Admur 469/2
 Stam opinion in Admur ibid; Taz 469/2
The reason: As the observer certainly will not come to think that one is sanctifying the food to use to buy the Pesach offering, as the food has no connection to the Pesach offering, as it is not a species of meat at all. [Admur ibid; Taz ibid]
 Machmir opinion in Admur ibid; Elya Zuta 469
 Admur ibid; Michaber ibid; Pesachim ibid
The reason: As by such items the onlooker will think one is saying they are for Pesach in order to hide them and guard them from Chametz for the sake of Pesach, [and not because he wants to use them as a sacrifice]. [ibid]
 Admur ibid; Chok Yaakov 469/1
 Admur 469/2; Parentheses in original
 The reason: As we do not forbid a food Bedieved simply due to Maaras Ayin. [Admur ibid]
 Stam opinion in Admur ibid; Taz 469/1; Olas Shabbos 469; Chok Yaakov
The reason: It is permitted to be eaten in all cases that the statement was made, as we never forbid something due to Maras Ayin. [Admur ibid]
 This applies even if it was said on Erev Pesach, after midday. [ibid]
 Stringent opinion in Admur ibid; M”A 469/2; Bach 469; Peri Chadash 469; Damesek Eliezer Chulin 82/19-15
 The reason: There are opinions who are stringent regarding goat/sheep, whether alive or meat, to forbid ever eating it, as the onlooker who heard him say “This meat is for Pesach” will think one has sanctified it as a sacrifice and that he is now eating Kodshim outside of the temple. This prohibition applies even to the meat, as the listener will think that the meat was already sanctified as a Pesach offering when the animal was alive. [Admur ibid]
 Admur ibid
 Admur ibid; implication of M”A ibid
The reason: As we do not forbid something in benefit merely due to Maaras Ayin, as explained in Taz Yoreh Deah 5/5. [ibid]
Other opinions: Some Poskim rule it is forbidden to even benefit from the meat. [Bach and Peri Chadash ibid]
 Admur ibid; Peri Chadash
The reason: As one cannot forbid something which is not his. [ibid]
 Piskeiy Teshuvos 469/1; Nitei Gavriel 2/4
 As writing is similar to speech. [ibid]
 Piskeiy Teshuvos 492/1