Q:

sync option in /etc/fstab

From the man pages of mount command

sync   All  I/O  to  the  filesystem should be done synchronously.  In
  the case of media with a limited number of write cycles (e.g. some
  flash drives), sync may cause life-cycle shortening.

Does this mean that when providing this option in /etc/fstab (given the following definition of sync command) 
$ sync --help
Usage: sync [OPTION] [FILE]...
Synchronize cached writes to persistent storage

...caching of contents (i.e. of memory pages created from the contents of the particular device) is prohibited?

A:

Read caching is not prohibited. Write caching is prohibited. In other words, writes to the device have to be done immediately, so there is no risk of data loss. 

