A conclusion is not a summary. Repeating what you already said adds nothing, and markers read a great many conclusions that simply restate the introduction in different words.
A good conclusion synthesises — it shows what your points add up to — and then answers the question a reader is entitled to ask at the end: so what? Enter your topic and this tool lays out that structure.
Summary says what you covered: "This essay examined X, Y and Z." Synthesis says what they mean together: "Because X constrains Y, Z becomes difficult to sustain." Only the second tells a reader something they did not already have.
The test is whether your conclusion could be written by someone who had only read your topic sentences. If it could, it is summary. Synthesis requires the argument to have been made first, and it shows.
A reader who has followed your argument is owed a reason it mattered. What follows for practice, for policy, for how the subject should be understood? One or two sentences is enough, but their absence is felt.
Keep the claim proportionate to what you actually showed. An essay analysing one case study does not license a sweeping recommendation for national policy, and overreaching at the end can undo the credibility a careful argument earned.
New evidence and new arguments. If a point deserves making, it belongs in the body where it can be supported; arriving in the conclusion, it looks like something you noticed too late to place properly.
Also avoid apologising for the essay, contradicting the introduction, and ending on someone else's quotation. The final voice a reader hears should be yours, making your own claim.
A sentence on what your argument does not settle reads as confidence, not weakness. It shows you understand the boundaries of your own claim, which is a mark of academic maturity.
Keep it specific and brief. "This analysis addresses only urban settings, and rural dynamics may differ" is useful. A paragraph of hedging suggests you do not believe your own argument.
Around 10% of the essay — usually one paragraph, and rarely longer than the introduction.
No. Anything worth arguing belongs in the body where you can support it.
You can, but it is rarely needed — the position on the page already tells the reader. Prefer opening with your restated thesis.
The opposite. A specific, brief acknowledgement of what your argument does not cover reads as control over your material.
Better not to. The last sentence should be your own claim, not someone else's words.