Question

Do with process
and find the resistance.

Answer 1

Due to symmetry accross A and C, there wun be flowing any current in OB and OD.
so, neglect these resistances.
this will become a parallel connection, as shown in figure,
Resistance bw A and C (R') 
1/R' = 1/2R + 1/2R + 1/2R 
=  3/2R

=> R' = 2R/3 ohm

Answer 2

this question can only be solved by using symmetry in resistance.
follow the process I did to answer this question to get the perfect answer