Richer's policy is clearly explained on the leaflet they clip your receipt to. You can return an item within 7 days, unopened and un-used, for a full refund. You can return an item within 30 days, used/opened, for a refund minus 15% re-stocking fee. In practise I have found them to be a bit more flexible than this, but I think you would need to make sure you agree anything outside the standard terms at the point of sale to save embarrassment/argument later.
Regarding demos, my view is that dealer demos in the demonstration room at the shop are virtually useless. You hear the equipment, but in a completely different acoustic space to your own room. Whilst it might help to compare different components that you hear at the same time in that same room, it doesn't really help you to work out how it will sound in your own room.
In my view offering home demonstrations is a central part of being a specialist hi-fi dealer. The best way is to build up a bit of a relationship with a dealer by doing some auditioning in-store, and then broach the subject of a home demo of the component you think might be best.