Upgrading Drupal

Hi
I took over a relatively simple project of a customer. When I checked the status I learned I ought to update from the present 8.1.8 to 8.4.2. I also learned that I have to update to 8.4.0 first.
Reading the info on https://www.drupal.org/project/drupal/releases/8.4.0 and going through comments in the forum I fell very uncertain if I 
- can download and install 8.4.0 from the above quoted link "easily" without a high risk to crash the (productive) site

Hi.  Thanks for looking at my post.  I'm wondering what the best, most efficient method or technique is to migrate a local Drupal 8 site, to a remote production site, and vice-versa?  I'm looking for something that isn't too difficult using the UI perhaps, but definitely not selecting files by hand and uploading to the web host.  Using Drush could be a possibility, but maybe difficult based on my limited experience.

Thanks so much,

Jason

I have tried to update drupal 8.0.5 to 8.4.2 but no success. I have tried it a couple of different ways. Direct update didn't work, so i tried going to 8.1.0 then 8.2.0, 8.3.0, 8.4.2, but it crashed when updating from 8.2.0 to 8.3.0. So i tried (found a suggestion) to 8.2.5 and also 8.2.8 but none of the updates worked. 
This was all done with option 2. https://www.drupal.org/docs/8/update/update-core-option-2

I'm trying to update acquia/lightning from 2.2.0 to 2.2.3 which updates drupal/core from 8.4.0 to 8.4.2. After executing 

drush updb

I get the following output:

Any help on this would greatly be appreciated. Thank you.

The update process was aborted prematurely while running update #8300 in block_content.module.
All errors have been logged. You may need to check the watchdog database table manually.

Hi

i am trying to upgrade drupal when i ran update.php (after doing previous steps such as disabling modules, copying new core files ...etc)

i got this error:

Warning: require_once(modules/fastpath_fscache/cache.fs.inc): failed to open stream: No such file or directory in /home/user/public_html/includes/bootstrap.inc on line 932

the module fastpath_fscache is actually disabled since long ago and i disabled all modules before adding the new core files