Question

Why lone pairs are placed on axial position in xef4 having significant repulsions?

Answer 1

This can be explained using VSEPR theory. In XeF2, there are 5 pairs of electrons around Xe and thus its geometry is trigonal bipyramidal. The flourine atoms occupy linear positions while the three lone pairs occupy equatorial positions. Thus, XeF2 is a linear molecule.
In XeF4, there are 6 pairs of electrons around Xe and thus its geometry is octahedral. The flourine atoms occupy the positions in the plane giving a square planar molecule. Two lone pairs are perpendicular to this plane.

Answer 2

is sp3d2 hybridization all bond length are same and angles are also equal so just image it as a 3d and rotate the molecule you will fund from any position you will get a square and two axial but actually the axial and equatorial concept you are using is for sp3d hybridization and not sp3d2 so you can place you atoms on any orbital and if you are finding lone pair on axial then rotate your 3d molecule the lone pairs will come to equatorial position

I used word equatorial and axial to explain you remember in sp3d2 you cannot apply bents rule so no equatorial or axial