Short answers with links to the entry that covers each properly.
On answers that expire
The honest answer to what the current address is stops being true. The honest answer to whether a market will exist next year is that nobody knows. Wherever those get answered confidently, the confidence is the product rather than the information.
Related questions
Which of the three addresses should I use?
Any of them. They reach the same market, which is what mirror covers. Whether the one you reached is genuine is a different question.
What does finalize early mean?
Releasing the funds before the order arrives, which ends the escrow arrangement on it. See finalize early.
Is my money safe in escrow?
Safer than the alternative, which is not the same as safe. It means the platform cannot move it alone, and five other situations are untouched. See in escrow.
A vendor wants payment outside the platform. Worth it?
No, and it is the only thing in this book with no recovery mechanism behind the wrong answer. See pay direct.
My deposit has not appeared. What now?
Check your own wallet before contacting anybody, because the answer is almost always visible there. See unconfirmed.
Somebody says they are support. Are they?
No. No market runs support on a messaging app, a forum account or email, so the channel settles it. See support here.
My old address works again. Is it back?
No, and it is the clearest warning here. Nothing retired returns under the same string. See gone.
How much should I keep on the platform?
Nothing you are not about to spend. See available balance, which describes the most frequent loss in this subject.
Why does this site publish no uptime figure?
Because it measures nothing, and a figure it could not back would be worse than none.
Is this site connected to the market?
No. It cannot recover an account, refund an order or act on your behalf in any way.