Slovenia is country code +386.
The country code and area code of Celje, Slovenia is 386, (0)3.
The country code and area code of Kranj, Slovenia is 386, (0)4.
The country code and area code of Krsko, Slovenia is 386, (0)7.
The country code and area code of Maribor, Slovenia is 386, (0)2.
The country code and area code of Kotor, Montenegro is 382, (0)82.
Leichtenstein is telephone country code +423.
where is telephone country code 1816
That is not a country code.
No. Many countries, prominently Russia, still recognize Kosovo as part of Serbia. See http://www.iso.org/iso/country_codes/iso_3166_code_lists/english_country_names_and_code_elements.htm
There is no 909 country code.
There is no telephone country code +897, nor +89, nor any other country code beginning with +89. There are no valid telephone numbers beginning with +89.
Gibraltar is country code +350.