Paris to Etretat - Public Transport

Hi!
I am planning a trip to Etretat from Paris, with 2 nights stay in first week of July. Unfortunately I cannot drive and plan to take public transport.

I found two options —

1. Train from Paris > Le Havre and then Bus 13 > Etretat
2. Flixbus directly from Paris to Etretat

My questions are -

• Has anyone done this trip recently with either option? What did you do and what was your experience? What would be the best option? (I am not too keen on private taxi from Le Havre to Etretat)
  • Is the bus from Le Havre to Etretat reliable? Do I need to book this in advance?
  • How is Flixbus from Paris? (I have never taken one before)

Also, if anyone knows -- how feasible it is to do a trip via Rouen (have lunch and spend 2-3 hours exploring city), on the way back from Etretat to Paris? (again, with public transport)

Thank you!!!! :)