It is true that purely from an academic viewpoint, labour before 37 weeks is considered pre-term. However in practice it is rarely, if ever, necessary to treat delivery after 34 weeks. Most cases of pre-term labour occur in the period 28 to 32 weeks.
Duvadilan is the brand name of a medicine called isoxsuprine. With the launch of better, more effective agents with lesser side effects, isoxsuprine use has been discontinued.
Drugs in vogue are ritodrine and salbutamol even though some clinicians also use steroids, nifedipine and even magnesium sulphate.
Measures to arrest labour have to be taken when such an event occurs, not as a preventive tool. The fact that there has been a previous history of pre-term delivery (even though I do not consider 35 weeks 5 days to be pre-term) does not mean it will happen in subsequent pregnancies.