Hello,
1. Yes
2. There is no problem, as Xavier said :
You have two urls because many menus allow to reach that product page. If you want a unique url, so you have to remove a menu.
This behavior is a common one, most of ecommerce websites have many urls for one product.
3. 4. If you're worrying about your SEO :
If you are worry about the SEO, you can change the canonical urls settings in the HikaShop Configuration.
Canonical urls allow to give only one url for the robots which are parsing your website.