Adverb placement: is it rule based or just how you use the symbol

Question

10 years ago/later, which is 2010, the Avengers fought/ fights the villian Thanos.

who else wants the burger? why else would he do that?

Why are the adverbs later, ago, and else placed after 10 years, who and why?

i think 10 years is a noun phrase modified by 'ago', the adverb and because you can modify it with an adjective clause, 'which is 2010' from the sentence.

The same goes to the other sentence. Why is the adverb placed after the word it is modifying?

What does the rules say or is this just how we use it?

Answer 1

ten years ago and ten years later and a few others call for the simple past tense or another past tense. They are set phrases. The define a time period which is past or over. These set phrases cannot go with the present tense unless you are using the literary device of the historical present.

• They left ten years ago.
• Ten years later, they fought the villain.

Also, a few others: Ten years earlier or ten minutes sooner.

• Ten years earlier they did not fight them.
• Ten minutes sooner was not an option.