A question about fibre+homeplugs

[#1]

A friend of mine has recently got fibre but wants to move their P.C  and router upstairs out of reach of the modem, Is it possible to connect the router to the openreach modem via homeplugs?
Phone line>Open reach modem>Homeplug1. Homeplug2>Router>PC etc

[#2]

Hi pint,
Theoretically this should be fine however it's possible that it could cause unwanted side effects so I it would be worth giving it a try, ideally with some borrowed home plugs before buying their own.
On a side note with this, if there are any issue/fault with the connection while in this configuration (regardless of the home plugs being the cause or not) it will have to be returned to the correct set up for the fault finding process in order to avoid any unwanted engineering charges.

[#3]

Could they not leave the modem and router downstairs, then homeplugs up to the PC from there?

[#4]

My homeplug master is connected to the router.