Graph Mode. The standard version corrects pitch automatically across a whole performance using a key and a retune speed. Pro adds note-by-note manual editing, so you can drag one word into place and leave the rest untouched. If you are fixing individual notes rather than treating a whole take, you need Pro.
No, and it stopped being a useful question about twenty years ago. Nearly every commercially released vocal since the early 2000s has been pitch corrected, usually so lightly you would never hear it. The audible, quantised effect is a deliberate production choice, not a mistake. Both uses are legitimate.
You need to know the key of your track. Auto-Key works it out for you and sends it straight to Auto-Tune. If you can identify key confidently by ear you can enter it manually and skip Auto-Key.
Auto-Tune Unlimited is a annual subscription and includes every Antares plug-in. Auto-Tune Pro 11 is a perpetual licence. The subscription wins in year one and loses by year three, and it gives you the whole catalogue rather than one title. Choose the perpetual licence if you want one tool for years; choose the subscription if you want the range or your work comes in bursts.
VST3, AU and AAX on macOS and Windows. That covers Pro Tools, Logic Pro, Ableton Live, Cubase, Studio One, FL Studio, Reaper and Bitwig.
It fixes pitch. It does not fix timing, phrasing, poor mic technique or a performance without conviction. A flat note becomes an in-tune flat note. Correcting a take that is badly out will also produce audible artefacts, because the further the software has to move a note the more obvious the processing becomes. Record a better take where you can.
Harmony Engine generates separate harmony parts at intervals you specify, following your chord progression. Choir multiplies the same part into up to 32 voices with small variations in pitch and timing, which thickens a line rather than harmonising it. Different jobs.
By email, as a serial number with a download link, once your order is processed. You register it to your Antares account and download from there.