A:Since you were working on convergence issue from past couple of days I would like help you beyond the scope of academic support. Please read the support related guidelines mentioned at the end of email.
I am attaching the case and data file which should run without any issue.
1) I have changed the solver setting a bit. Using SIMPLEC algorithm.
2) Hybrid initialization is used.

Please let me know if you have further questions.
Please take the time to review the scope of academic support. This information will help you understand what type of assistance to expect.

The time step size set in case file it too large for this kind of unsteady simulation. We need to use small time step size so that the time step should be no larger than the time it takes for a moving cell to advance past a stationary point at interface regions. A dt =1e-4 s should be good in our case.
please refer manual
1) requirement and limitation of sliding mesh : help/flu_ug/flu_ug_sec_slide_grid_req.html
2) Solution stratergies of sliding mesh : help/flu_ug/flu_ug_sec_slide_solve.html

Fluent can handle larger aspect ratio. For some external aerodynamics case even 50000 will work . I think 200 should be alright for this simulation and we can proceed with it.