Don't know of any new full suspension bikes for $400. If anyone is selling you a brand new FS for that price I'd stay well away. If you really want a FS you'll have to up your budget by a few hundred.
Since you're posting in the beginner forum I'm guessing you're a beginner, so you might just want to start out with hardtail. Cheaper, can get better components and will still give you lots of fun. You can check out the main retailers...specialized, trek, giant, iron horse, kona, k2. I've never ridden on any of them with the exception of specialized. In the meantime, you can have time to educate yourself on the types of full suspension types there are, the types of bikes that are out there, etcetera...the last thing you want to do is find yourself with a craptastic bike because you rushed into it.
I went from a fully rigid to a FS in a spur of the moment and somewhat regret that purchase as my riding progressed into something that my FS was not designed for.
Sorry to hear of your derailleur hanger getting snapped off. That can happen sometimes, even on a full suspension.
I've never ridden the specialized hardrock sport, so I can't really comment. Maybe you can do a search of the beginner forum and the specialized manufacturer forum for the hardrock sport or solicit others' opinions.
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