Initial resistance, R0, is 10 Ω. Upon stretching to length 2l, the resistance R1 becomes $\frac{2l}{l}$R0 = 20 Ω. Bending into a circle does not alter the total resistance, which remains 20 Ω.
The resistance of a semi-circle along any diameter is calculated as 20/2 = 10 Ω.