Line Tools takes a list of lines and reshapes it: sort, reverse, shuffle, dedupe, drop blank lines, trim whitespace, number each line, or add a prefix and suffix.
It runs in the page. Nothing you paste is uploaded.
It orders numbers inside text the way people expect, so item2 comes before item10.
The first by default. There is an option to keep the last one instead.
If you set a seed, yes. The same seed shuffles the same way. With no seed it is random each time.
No. Every operation runs in your browser.