Who has to file service tax return

Yeah...nil return should have been filed even if there is no tax liability. Since it is not done, penalty is applicable as per sec 70(1)

evry one must file return,Who has registeration under Service tax

but the below attached link says that "Persons who are not liable to pay service tax  (because of an exemption including turnover based exemption), are not required to file ST-3 return."

please refer to para 6.1

https://www.servicetax.gov.in/circular/st-circular07/st_circ_97-2k7.htm

Refer rule 7C of Service Tax Rules: https://www.servicetax.gov.in/st-rules.htm

Provided also that where the gross amount of service tax payable is nil, the Central Excise officer may, on being satisfied that there is sufficient reason for not filing the return, reduce or waive the penalty.

So it means penalty is applicable.