Q: can i unlock my icloud lock which phone imei is lost mode , how or why not

Hello Nantubd, 

Thanks for using the Apple Support Communities!

From your question, it sounds like you iPhone is either in Lost Mode or in an Activation Lock status. The following articles explain both of these features in more detail. 

Find My iPhone Activation Lock - Apple Support

iCloud: Use Lost Mode

If these articles do not provide the information you need, please provide more details about your situation so we can provide further assistance. 

Cheers!