Originally Posted by Jeremy Bender
Thirdly, I really don't know if the stores allow customers to change the strings on guitars,
generally - no they don't. There can be exceptions - if say it's a teaching shop and you are an advanced student moving up levels or if you have a relationship (ie you are a reliable repeat customer) and you a pretty far along in the purchasing process (and the instrument is expensive enough)
Though even there it's probably more common in say the classic[al] guitar specialty shop than your avg rock-n-roll electric guitar shop
I do know they're allowed to try them with an amp and effects.
that's more akin to try different modular system components such as a kick pedal or cymbal set or drum brain - as no individual module is being reconfigured (changing the action or strings on a guitar, retubing an amplifier or altering an effect through trimpots or component swaps etc)
[interesting note on guitars - they aren't really in tune or not]