Of course yes, anyone can used bitcoin, even the student, vendor or ordinary people. Even the rich level of people allowed to used bitcoin. Because bitcoin is for anyone or for everyone.
Yes. Everyone is free to use it. No one can use it. I think those people who has lack of money is the most people who needed to use and learn how to use it. Bitcoin might help us very much. It can save them for not having a food to eat. They only need a cellphone for them to earn bitcoin and thats it.
No one forbade you to use bitcoin. Whoever you are from wherever you are, poor or rich you are free to use bitcoin. As long as you have gadget to access bitcoin then you can use bitcoin. No rules so you're free to use bitcoin.