Is there a DOCIS 3.1 model that includes a RJ11 phone jack

> Is there a DOCIS 3.1 model that includes a R11 phone jack.

   Why would a cable-TV network modem have a telephone connector?

   Is there some actual problem which you are trying to solve, or some
actual requirement what you are trying to meet?  

   It might help if you started at the beginning, and explained what
you're actually trying to do, rather than asking how to implement some
"solution" to whatever problem you think that you have.

> [...] what kind of experience does anyone have using the RJ45 to RJ11
> adapter and connecting through the router.

   I certainly have none.  I have no idea why you'd want to do anything
with some (unspecified) kind of "the RJ45 to RJ11 adapter".