Pesachim 9:6

R’ Akiva says that if a korban pesach was lost and you took another animal and then found the original animal, you should wait until it gets a blemish, sell it and use the money to buy a korban shelamim. The same is true with a korban pesach temurah [where you tried to substitute the korban pesach on another animal]. This is all before shechita occurs but after shechita the missing korban is brought for a shelamim and the same with a temurah.

Pesachim 9:7

If you set aside for a korban pesach a female or a 2 year old male animal which is not good for a korban pesach, you should let it pasture until it gets a blemish, then sell it and use the money for a korban that is a present such as an olah.

If someone set an animal aside for a korban pesach and then died, the children bring the animal for a shelamim.

Pesach after they left Mitzrayim is a Yom Tov for 7 days.