Yes, if you get into the CT late morning on the 6th, you can do all 5 villages. Drop your luggage at your accommodation (stay in the same place both nights) and just take off.
You could, say, knock off two villages and a hike on the afternoon of the 6th, weather permitting. If you stay in Monterosso, you could hike to Vernazza on the 'Blue', explore the town and take a train back. Do it in reverse if you stay in Vernazza. Next day, take a ferry to Riomaggiore, a train to Manarola, train to Cornigila, and hike the 'Blue' from there to Vernazza. Take a train back to Monterosso. There are any number of ways to cover cover ground so this is just one suggestion, and some flexibility might be in order in case the weather doesn't cooperate for hiking.
Corniglia is up on the cliffs above the train station so it's reached via a long switchback stairway or a little bus (small fee) that's timed to meet the trains: the fee is covered by the Cinque Terre Trekking Card which you must have to hike the 2 open sections of the Blue Path (SVA2 Sentiero Azzurro.)
If you only want to buy a 1-day trekking card, then do Monterosso>Vernazza>Corniglia on the 'Blue' on 8/7, weather permitting. There are many other trails in the park but 'Blue' is what most tourists come for.
If you haven't found it yet, this is the park's website:
http://www.parconazionale5terre.it/Eindex.php
Info on the trekking card:
http://www.parconazionale5terre.it/page.php?id=157
Ferry schedules for Oct. aren't out yet but keep an eye on this site:
https://cinqueterreinsider.com/2018/03/22/cinque-terre-ferry-schedules-2018/
(Edited to correct an error)