if they are in opposite direction then there is an inversion of element and if they are in same direction then deletion of the element

There are already such pDONR vectors which attPs signals in same direction (ex. pDONR P4P1R, pDONR P2R-P3). It is true that they seldom recombine each other and deletion of the element between them occurs as Ngarjun mentioned above. But it happens by rare homologous recombination event in host bacteria. In usual Gateway reaction, att signals with different number does not recombines but with the same number does. In the case of pDONR P4-P1R, you should amplify a PCR fragment flanked with attB4 and attB1 in same direction. (It means that the reverse PCR primer should have a reverse oriented attB1 signal at 5' end.)

To answer Poonam's question directly, if one of the attP or attB signal of the pDONR or attB-PCR fragment was not in right direction in BP reaction, the resulted product cannot be a circular plasmid so that we obtain nothing.