Answers, without the runaround.

Zip it first. A folder dropped into the upload card is skipped, because browsers cannot read a directory the way they read a file.

No. Chunks that already landed are kept. Reconnect and the upload continues from where it stopped. If you closed the tab, re-add the same files and it will pick up the parts that are already stored.

Not to a transfer that is already uploading. Finish it, then create a second transfer — or cancel and start again with everything selected.

Programs, scripts and installers are blocked for everyone's safety. If you genuinely need to send one, put it inside a ZIP archive.

No. Open the link and the files are there.

Very large transfers are downloaded file by file instead of as one archive, because a single archive that size is fragile. The page switches to a queue automatically and tells you it is doing so.

Files are deleted permanently at expiry and cannot be recovered. Ask whoever sent it to create a new transfer.

Only the sender has it. We cannot reset or reveal it, because we never store it in a readable form.