Importance of Collatz conjecture [on hold]

My following two questions on Collatz conjecture are rather vague but (I think) important if one wants to take time on it.

Q1. What are the difficulties and challenging parts to attack the problem? What field of math can possibly provide required machinery? The problem has been open since 1930~, and our beloved mathematics has been developed significantly since then.
Q2 If the conjecture proven true, what are some consequences in different areas of math such as finite groups, prime numbers,dynamics etc.

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