The correct answer to this open question is the following.
You do not include any context, reference, or a specific event in history. So we assume you are talking about general terms.
Does universal suffrage mean anarchy or mob rule?
No. Universal suffrage means that every citizen has the right to exert its right to vote.
“Who should be a citizen?”
Every single individual who was born in the country or the individuals that comply with the requirements established by the law.
A source that has a position most like my own is the Constitution that clearly expresses who is a citizen and the requirements to become a citizen.
In democratic nations, universal suffrage allows every citizen to participate in elections and vote. In these democratic nations, people also have a series of rights that allow them to freely express themselves, elect their rulers, have a religion, property, and gather with family and friends.
There are also rules and regulations to avoid any disorders or conflicts between citizens. So in democratic countries, you have rights but also, obligations.