Full text search is an optional component of the SQL Server Database Engine. If you didn't select Full text search when you installed SQL Server, run SQL Server setup again to add it.
Full-text search component can be selected from the available features list, when adding new features to the existing MSSQL server edition. Availability of the full text search component depends on the SQL server edition (see the table below).
Features supported by the SQL Server Editions
MS SQL Server is using 'English' language by default, list of options in the MSSQL full text languages documentation.
$CFG->dboptions['ftslanguage'] = 'English';
$CFG->dboptions['ftslanguage'] = 'German';
$CFG->dboptions['ftslanguage'] = 'Japanese';
$CFG->dboptions['ftslanguage'] = 1028; // Traditional Chinese
$CFG->dboptions['ftslanguage'] = 2052; // Simplified Chinese
Minimum search term length
MS SQL Server don't have specific default length and may find the words as long as it's a dictionary word.
Stop words is a dictionary of words that will be excluded from index and search query. They depend on language being used during indexing and search as well as dictionary presence for database installation.
eg: if user search for "Hotels in Wellington" then the system excludes "In" words from the search.
More details on MS SQL Server 2017 stop words can be found in Microsoft's SQL documentation.