Cylinder number confusion

ChatGPT is frequently wrong when it comes to automotive items, especially diagnostics.
P0354 is a cylinder 4 coil secondary circuit failure, usually a shorted coil. Cylinder 4 is the middle cylinder on the radiator side of the engine as you indicate. The DTC sets when the ECM doesn't get the feedback signal from the coil(s) indicated. That is commonly from a failed feedback circuit in the coil. The easiest way to confirm it's the coil and not a wiring fault is simple, swap the coil with a neighbor cylinder. The code should follow if it's the coil. Remove the engine cover and in the middle of the left cylinder head you will find the coils. Remove the retaining bolts and lift them out and swap cylinders 4 and 2, Connect them up and start the engine. If you now have a P0352 you have a bad coil. One thing with Toyotas and Hondas are that they are touchy about replacement parts, I have seen aftermarket parts from quality companies cause problems on them that an OE part cleared up as soon as it was installed, as such I use OE parts on the ignition and control parts of those brands.

I've never used any apps so cannot say if any are better. I just keep attending training and networking with other techs and stay updated on the automotive repair items. Been doing the job hands on close to 50 years myself. There are a few folks I could point you toward if you really wanted to learn, but don't know of any apps.

Current OE coil part number is 90919-A2013 Fits a LOT of Toyotas with the 3.5 in them from 2005 to 2024 If you have a you pull it type yard, I would go there and find a newer
Camry, Highlander, Avalon, Sienna that is wrecked and grab the coils off the front of a couple. Plug wise, I would look at when they were changed last, The service table shows a Denso 3426 FK20HR-11 that gets changed every 120K so you are probably due unless all 6 were changed recently. The catch is that changing the rear 3 is a pain because you need to pull the intake off to get to them. However it does give you the chance to inspect things that are normally hidden. This might help -
https://www.youtube.com/watch?v=ING-RK7NJ-c

I take classes when possible, but online is usually easier. These are a few of the ones who have classes or videos where you can watch them work and see if you do something different. There are also various free classes from places like O'reily and Worldpac.

Advanced Level Auto, Autel North America, Automotive Diagnostics & Programming, Automotive Test Solutions, FordTechMakuloco, CDS Automotive Diagnostics and Repair, Cody Gaddie, DeadOnDiagnostics, Garage Gurus, GoTechTraining, Joe's Auto Electric, L1 Automotive Training, LM Auto Repairs, McCuistian, MotorCity Mechanic, New Level Auto, One Auto, Opus IVS, Oz Mechanics, picoautomotive, Pine Hollow Auto Diagnostics, Pinpoint Automotive Repair, Positive Lead Diagnostics, Rainman Ray's Repairs, Robert Dotterer, ScannerDanner, Schrodingers Box, South Main Auto, Trained by Techs, TSTseminars, Vehicle Service & Repair Video Network, Voltage Drop Diagnostics, WeberAuto and 2carpros repair guides and youtube.

They are all good places to learn and some actually offer classroom training as well as the smaller online items. I would recommend getting Paul Danners book as well, it teaches a lot of things and has videos if you opt for the online version (which can be printed to pdf). TST does big training events and Weber auto is part of a full degree course at Weber University. GoTechTraining is good for a lot and the trainer was part of Wells Vehicle Electronics. Some of them stopped making videos but the ones still up are great to learn from. There are a few others but I figure those would get you started. Then if you wanted classroom style training there are places like NAPA, Advance, Fisher that list training classes in the professional side of their sites. Plus TSTs Big Events, VISION and a host of others where you register and pay for a day or week for training seminars. If you are on youtube, facebook, instagram you can join places like Diagnostic Network and they have training and online talks where you can get involved. I only wish these resources had been around when I started, but someone had to carve Freds wheels out of bedrock. LOL