/n/ is realized as [ŋ] before /k/, but this is not distinguished phonemically.
Only as allophone of /Ng/.
An allophonic /ŋ/ might occur in free variation when n is before a k.
the velar nasal is used in interjection only, not used in content or functional words
Except as allophone of /n/ before /k g/, unsurprisingly.
A velar nasal can be inserted after nasal vowels before /k/ and /k'/. However, this is optional and rather a result of assimilation processes. Example: canka /tɕãka/ - street [cã:ka] or [cãŋka]
Occurs only as allophone of /n/
[ŋ] is present as the realisation of/n/ in coda position.