What should be done with a sacrifice that is in doubt of being invalid (in a regular case)?
It is established in halacha that in a regular doubt of invalidity, one waits until the next day for certainty, and then burns in the courtyard.
Question 2
When do you burn leftovers and piggul?
Burning leftovers and piggul is specifically during the day, as learned from the verse that burning occurs on the third day during the day and not at night.
Question 3
Does burning impure/leftover/piggul override Yom Tov or Shabbat?
Rambam rules that these burnings do not override Yom Tov, and certainly do not override Shabbat.
Question 4
A person leaves Jerusalem and remembers they have light sacred meat; if they have already passed Tzofim — what is the law?
After passing Tzofim, one burns in their place; beforehand, if there is a kezayit, they return to Jerusalem to burn.
Question 5
Why should one not burn something that requires burial?
Rambam explains that burning something that requires burial is considered a leniency regarding ashes, as the ashes of the buried are prohibited for benefit.