Questions about bitcoin(or other crytocurrency) to satisfy my feeble mind
Cloud mining is generally only profitable for the Operator (otherwise they would mine themselves instead of selling their hash power).
Your account or the exchange getting hacked, or the exchange deciding to suddenly close (perhaps also claiming to be hacked) and taking your funds. If you buy coins on the exchange always use 2FA and take the coins off of the exchange (send to your own cold wallet) as soon as possible.
You can start with as little as you wish. Focus on learning at first. Large, quick profits are very unlikely for a beginner with limited funds. Most "traders" lose money because they are less informed than coin developers/promoters. Focus on code you can see in GitHub, not what developers are promising to deliver in the future.