1. The GRE has three types of questions: reading, math, and writing. You should look up some sample tests and see what kinds of questions it asks.

2. You are free to get whatever degree you want after a Bachelor's degree (BA or BS). That means you can get a Masters (MA or MS), or any other kind of degree (law, medicine, public health, public policy, social work...etc). You just have to get admitted to the degree program.

3. It depends. Some programs are not directly related to your undergraduate degree, so you may want to get some experience to see if that's the field you want to go into. Other programs are a continuation of what you learn in your undergraduate program, so it may make sense to just continue into the higher degree.

4. A graduate degree is a significant investment in time and money, so not as many people will be interested in pursuing one, and really, you shouldn't be pursuing it unless you were interested. Some programs will be more competitive than others, just like undergraduate programs.