Twelve lists of ordered abbreviations are given below. The first part of your mission is to find out what comes next in each of them. Further instructions will await you once you have completed this first task.
$$\begin{array}{align*} \textbf{ 1 }&\text{ $\implies$ }&\text{AL, AT, DR, FY, JY, JY, ?}\\ \textbf{ 2*}&\text{ $\implies$}&\text{SR, OR, NR, MY, MH, JE, ?}\\ \textbf{ 3 }&\text{$\implies$}&\text{FR, CH, US, DE, CH, NO, ?}\\ \textbf{ 4* }&\text{$\implies$}&\text{BR, GB, CN, GR, AU, US, ?}\\ \textbf{ 5 }&\text{$\implies$}&\text{NY, MD, GA, ME, TX, LA, ?}\\ \textbf{ 6 }&\text{$\implies$}&\text{PE, AB, NB, NS, NU, QC, ?}\\ \textbf{ 7 }&\text{$\implies$}&\text{JA, JQA, CAA, JB, GHWB, GWB, ?}\\ \textbf{ 8 }&\text{$\impliedby$}&\text{BO, JAG, GC, GF, FP, CC, ?}\\ \textbf{ 9 }&\text{$\impliedby$}&\text{AS, ZN, PB, AU, I, BR, ?}\\ \textbf{ 10* }&\text{$\impliedby$}&\text{HG, SB, CO, P, S, AG, ?}\\ \textbf{ 11 }&\text{$\implies$}&\text{MHALL, LL, LL, MHALL, WFWWAS, AETMW, ?}\\ \textbf{ 12 }&\text{$\implies$}&\text{AYS, AYS, BJ, BJ, MBAR, MBAR, ?}\\ \end{array}$$
Fill out your answers in the grid below and please note that they are not in numerical order.
Once you've found the answers and filled the grid, follow the steps below to complete your mission.
Step 1:
In the grid, after which numbers might the characters ':' (I) and '&' (II) follow?
Combine these numbers -(I) and (II)- to form (III) and divide the second key by (III).
Now, take the square root of the number you've just obtained and call the result $n$.
Count off every $n$th character of the message below. When you reach the end, start again from the beginning, until you again have a 33 character message (the question mark does not count and stays at the end).
Step 2:
Reverse the first key and transform (5,4) to obtain a final nine-letter key.
Use the resulting key to decrypt (Vigenère) the rearranged message from Step 1.
Add spaces and punctuation to find the final question.
Finding the answer to this question will complete your mission.
Message:
UDTCMIOLRQIFCIAITAHSZARORHREKVAOC?