  In this paper we first address four point functions of string amplitudes in
both type IIA and IIB string theories. Making use of non-BPS scattering
amplitudes, we explore not only several Bianchi identities that hold in both
transverse and world volume directions of brane, but also reveal various new
couplings. These couplings can just be found by taking into account the mixed
pull-back and Taylor couplings where their all order alpha-prime higher
derivative corrections have been derived as well.
  For the first time, we also explore the complete form of a six point non-BPS
amplitude, involving three open string tachyons, a scalar field and a
Ramond-Ramond closed string in both IIA, IIB. In a special limit of the
amplitude and using the proper expansion we obtain an infinite number of bulk
singularities that are being constructed in the effective field theory. Finally
using new couplings we construct all the other massless and tachyon
singularities in type IIA, IIB string theories. All higher derivative
corrections to these new couplings to all orders in $\alpha'$ and new
restricted Bianchi identities have also been gained.
