I want to give UPLOAD FILE OPTION on product detail page where customer can upload files and admin can get files from backend. is it possible?
Yes it's possible.
Look at the "Custom options" section.
When you edit a product in the backend, there is a tab called "Custom Options".
Open it, and click on the "Add new option" button on the top right of the tab.
This will show you some fields that you have to fill in.
One of them is "Input Type". Select
File, fill in the rest of the fields and see what happens in the frontend.
yes you can add a custom option to product and its type should be "file". Magento will automatically show a upload file option before add to cart button on product detail page and uploaded file will be automatically available to store owner in order detail page in admin.