External memory can be troublesome. No one said you can't download apps. There are thousands of apps you can safely download and use without problems. You need to remember that most of these apps are developed by 3rd party developers and nothing to do with Nokia. Skype should be fine. Anti virus is not necessary so you are only wasting space with that. Whatsapp from my experience is troublesome on any platform. Try something else if you can. I also suggest installing apps one by one so you can isolate the trouble maker and report it to the developer.
You won't need anti virus as long as your downloaded from a reliable source. All apps from the Store as fine.
I think you had a bad experience with one bad installation. Install a few more apps, one at a time and see how the phone reacts. I am sure they will be fine.
Also, is your phone on Symbian Anna or Belle and have you checked and installed updates yet?
If the problem persists then by all means throw it.
That is a decision only you can make. If your phone is working properly it should not be hanging all the time. If resetting sloved the hanging then it was probably caused by one of the apps. If you can live without the app then perhaps you should keep the phone. If you still have a priblem with it then perhaps you should return it. The decision is yours.
