Two interleaved letter-number series, one going forward and one backward (G7, T20, H8, S19 ...)

This type of question, asked 3 times: 23 Sep 2025 S1, 24 Sep 2025 S2, 26 Sep 2025 S1. All 3 questions below, oldest first.

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Question 1
23 Sep 2025 S1
11 $What comes next? B25, Y2, C24, X3, ?$
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Question 2
24 Sep 2025 S2
16 $What comes next? G7, T20, H8, S19, ?$
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Question 3
26 Sep 2025 S1
20 $What comes next? C3, X24, D4, W23, ?$
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