I am trying to learn results related to the presentation complex of a group and I am new to this subject. So I apologize if the questions are silly. 

Given a finite group $G$, and a presentation $P$ of $G$, consider the presentation complex $X_P$. I have computed using the Mayer-Vietoris sequence for the group $S_3$ (the symmetric group of order $6$) and get $H_2(X_P,\mathbb{Z})\neq 0$ (in fact it is torsion-free). Also, by using a similar method I was able to show that for finite cyclic groups $H_2(X_P,\mathbb{Z})=0$. I have the following questions: 

1. Is $H_2(X_P,\mathbb{Z})$ always torsion-free for a finite group $G$? 

2. Can we put some restriction on $G$ (here $G$ is a finite group) so that $H_2(X_P,\mathbb{Z})\neq 0$? 

Any suggestions will be really helpful.