Is there anyway to identify the type of squash you are growing from the leaves, flowers or fruit?
There are so many different types of squash, and although there are differences in leaf shape, colour and growth habit they are relatively subtle and it's very hard to make an identification from that alone.
You would be very unlucky to have finished up with an inedible ornamental gourd - you can't really 'over-mature' a squash or pumpkin on the plant, just look for signs that the stalk is starting to shrivel and the skin is very hard, then harvest to eat or store (certainly before the first frost strikes.)
When it is mature you may be able to match it up with a named variety by doing a Google image search (the fruits are a bit more easy to identify than the plants themselves.)