I don't know why the past tense is used after the phrase "until after".

Is there any difference in nuance between "instead" and "instead of"?

Good question, yes, there is a difference between "instead" and "instead of", however, it is mostly a difference in grammar. "Instead" is an adverb that is normally used at the beginning or end of a sentence to mean "as a replacement to" or "as an alternative to". The phrase "instead of" is a preposition used to show that one thing replaces another. "Instead of" is always used in the middle of a sentence. Ex: I made some coffee but now I want tea instead. Ex: I drank tea instead of coffee.

What does "pumpkin" mean? Is it like "honey" or "baby"?

Yes, the term "pumpkin" in this case is a term of endearment similar to "honey" or "sweetheart". It is often most common to use for children, but it can be used for adults as well. Ex: Are you ready for your first day of school, pumpkin?

What is the original form of "shadow's", "shadow has" or "shadow is"?

The original form of "shadow's" in this situation is "shadow has." Peppa is speaking in the past tense about how her shadow went away and that she misses it. If the original form was "shadow is" the sentence would have to be "I'm a bit sad that my shadow's gone."

What's the main difference between an ordinary bank and the "central bank?"

Here, the two banks would be the "central bank" and the "commercial," or ordinary, bank! The difference between them is that the "central bank" does not operate for profit, whereas a "commercial bank" does. It also differs in its client. The "central bank's" client is the government and other commercial banks. A "commercial banks" clients are businesses and individuals. Ex: The commercial banks here offer loans to their customers. Ex: The central bank helped regain some of the country's economy.

What's "in our favor" mean?

"In our favor" means "to one's advantage," when something or someone works to help or benefit someone in a good way. In this case, "the light changes in our favor" means that the light turned green, which was good for the speaker. Ex: The score is in our team's favor. Ex: He turned the argument around in his favor.