I asked some questions about finite Cayley graphs with special type of subgraphs which has been answered by Dear Prof. Godsil. It can be seen in the MO page with address:

http://mathoverflow.net/questions/84898/cayley-graphs-and-its-subg

But there are some new questions which is interesting for me if there are some answers for them. 

$1)$ Are there infinite $r$-regular Cayley graph which all its induced $s$-regular subgraphs are Cayley? (non-trivial cases such as $\cup_1^\infty K_2$ or such as @verret introuduced.)

$2)$ Are there infinite $r$-regular graph (which is not Cayley) which all its induced $s$-regular ($s<r$) subgraphs are Cayley?

$3)$ Let $\Gamma_G^S=Cay(G,S)$ be a finite (or infinite but $r$-regular) Cayley graph and $\Gamma'$ be an induced Cayley subgraph of $\Gamma_G^S$. Can we describe the subgraph $\Gamma'$ by some quotient of $G$ or by some its subgroups?

$4)$ Find all groups $G$ (finite or infinite), in a such a way that for arbitrary normal subgroup of $G$, say $N$, the Cayley graph $Cay(G,S)$ has an induced subgraph isomorphic to $Cay(\frac{G}{N},\overline{S})$, where $\overline{S}=SN$.

I appreciate any answers and references for these questions.