4 Day Cinque Terre Itinerary

Take the ferry to Porto Venere.

https://photos.app.goo.gl/pWeqtcdCWzFX4HXu9

Hi - your post mentions “Montessaro” several times, but I’m guessing you’re referring to Monterosso, the largest, and northernmost of the 5 towns.

We visited 2 years go, also staying in an Airbnb in Riomaggiore, our favorite of the five. This was in early fall, and I must say that the crowds were so much bigger than our previous visit back in June 2001. Especially with the literally shoulder-to-shoulder mob in Vernazza (yes we were part of it), that’s probably our last time there. But I hope you enjoy your time.

When we were there, very recent rockslides closed the section of the Blue Path between Vernazza and Monterosso. I don’t know when it got reopened, but just like we were surprised by that news, you may or may not experience sudden changes in trail conditions. The section between Riomaggiore and Manarola, the so-called Via del Amore, had been closed for a long time, and I don’t know whether it’s been officially reopened. They bolted chain link material to the cliff faces to try and keep them from crumbling and showering boulders onto the trail, but apparently the danger continues to be a problem. We saw some people who hopped the locked trail gate, to gain access to rocks and cliffs overlooking the ocean. Whether closures are actually enforced, I don’t know, but if safety is the reason for a closure, then take it for what it’s worth.

If you make it to Corniglia (it’s a looooooooooong stairway descent/ascent, to/from the train platform), be sure to get gelato at Alberto Gelateria. They’re truly exceptional, especially their lemon basil flavor.

Porto Venere may very well get added to our day 3!

And thank you for the hiking advice. We want to be able to go all the way if possible.

You sort of hinted at this in your question, but you don't need to fill your days in the Cinque Terre. And you don't need to plan in advance.

The CT are not about sightseeing. You can do whatever you want on each day, build in time to just relax over a glass of wine, and see what the weather and your energy level and your mood dictate. You can hike the trails that are open and don't worry about which ones might be closed. If there's a trail that's closed, hike a different one. By all means get out on the water.

Planning hour by hour in the CT seems to me like you are missing the entire purpose of being there.

We took the train/bus to Porto Venere and then the boat back to CT. We had planned to hike there https://discoverportovenere.com/hiking-cinque-terre-riomaggiore/ and boat back but didn’t end up hiking that day.
This was our second trip to CT and Porto Venere remains one of our favorite places.

As you mention the Blue Path/Sentiero Azzurro several times...
This is the website for the park: it's going to be useful for trail descriptors, ratings, and which are open or closed at any given time.

https://www.parconazionale5terre.it/Eindex.php

This is a map of the trail system; click on any colored line to bring up its number and start/end points, and click on "View the Itinerary" to bring up details, such as length, difficulty, and description of landscape and landmarks along the way.

https://www.parconazionale5terre.it/Esentieri-outdoor.php

The trails on the map are color-coded: an orange line means the trail is strenuous; a black line means that trail is closed, and please be a respectful visitor and do not trespass around or over any barriers. Scroll down on the page to the few highlighted "Walking Itineraries" and you'll see they've highlighted all 4 sections of the SVA2 route...which is the Sentiero Azzurro/Blue Path. You'll see that currently all of those segments are closed. Montersosso> Vernazza, and Vernazza> Corniglia are closed to winter maintenance, and Corniglia> Manarola has been closed for years due to landslide; no idea when it'll open again. The stretch between Manarola and Riomaggiore - Via dell’Amore, which also had been closed for years - reopened on test basis last summer for guided tours only (5 euros; not included in the CT Treking or Treno card). I haven't seen yet what they've decided to do this season.

https://www.parconazionale5terre.it/Edettaglio.php?id=75005

So long story short, no, you can't hike from Riomaggiore to Monterosso on the "Blue"; you'd need to take alternate routes around closed sections. That's entirely possible; those alternates are usually just longer and more strenuous. Yes, your Treno card will cover hikes on the Blue, and also the local bus system. When using the trains, make sure you're using just the regionals; there are some others traveling though the region that the card isn't valid for.

https://www.parconazionale5terre.it/page.php?id=158

Hope this helps. Lastly, as mentioned above, there's no need for an itinerary other than maybe for restaurant reservations during busy seasons. Go according to whim and weather! :O)

The Via dell'Amore will reopen before summer according to the Regional President who said as much Jan. 20 during the production of this ad for Ligurian tourism. which encourages you to use some of that free time smooching:
https://www.facebook.com/lamialiguria.official/videos/1765455883931710
Besides seeing Portovenere, from the dock you can cross the channel on the local cheap and frequent boats and hike around the island of Palmeria. Take a picnic and enjoy the excellent views, goats, and quarries: Palmaria Hike

Besides the excellent ideas above, a daytrip to Camogli is feasible. Lovely town, less congested. Also a boat along the coast covering all 5 villages is nice. There are myriad hiking opportunities as well so if you would like to go beyond what you've read about, ask locally about paths other than the Sentiero Azzuro.

BTW, the hike to the Santuario is awesome. Tough uphill but rewarding views.

We've stayed in the CT twice. Our favorite day excursions were the ferry to Porto Venere, biking on the rails to trails alongside the Mediterranean through restored train tunnels from Levanto, and a train trip to Santa Margherita and Portofino. But we also loved having a chill beach day.