well Alt-coins are incredibly risky so i would put a 10 on that. However there is a lot of potential as the saying goes. As long as only a small amount of your portfolio is on that then you are fine.
They're not if you handle them carefully and only trade the trusted ones (LTC, ETH,...). All you need is a basic understanding of what trading is about. Recognize good trading opportunities and don't panic sell ever.
For a beginner trader, it's better to trade only which the market is more likely to be stable yo prevent huge percentage of money lose. However, as you know everything and you are seeking for high inflation altcoins, you may try new coin which has a huge potential to pump rapidly or gradually for bigger profit. This is quite risky yet if it is understood clearly and you are updated on its market, it would be easy for you to avoid money loss but you get profit instead.
You're probably right there but that's the gready way. I personally try to find more sustainable opportunities rather than a one time pump and dump. But is the potential risk really worth the reward, even if you know the coin well it may go either way.