This is my fifth batch of sequence puzzles that are nasty and hard to solve; yet, each of them has a clear and justifiable solution.
Sequence 1:
T?M, AOT?, ROT?, AN?, T?SB, ROT?, TFA
Sequence 2:
5, 12, ?, 14, 11, 8, 16, ?, 19, 3, 17, ?, 15, 10, ?, 13, 4, 18, ?, ...
Sequence 3:
T, u, b, d, l, ?, ?, ?, i, b, o, h, f
Sequence 4:
A, P, ?, L, S, A, P, A, ?, B, L, H, M, R, T, ?, M, M, M, ?, ?, ...