How to Proceed with Next Step in Sponsorship (Cambodia to Canada)

Hello,

I'm currently assisting my parents with their sponsorship applications. They are currently in the process of sponsoring over 3 orphaned nieces, who at the time of the initial applications were 16, 17, and 17 years old.

We completed the first part of the application and received the application for permanent residents for their nieces, which we also filled out with them and sent to the Canadian High Commission in Singapore.

The visa office has responded to one of our nieces with requests for more documentation from her. The documents they are requesting are listed below:

1) Home Study report conducted by a competent authority. In Canada, a competent authority includes provincial or territorial authorities and individuals authorized by those authorities, such as an accredited social worker.

2) Letter of No Objection issued by the Ontario Ministry of Community and Social Services (it will be sent directly to us by the provincial office in Canada).

3) Approval letter issued by the Council of Ministers in Cambodia.

4) Adoption certificate issued by the Ministry of Social Affairs Labour and Vocational Training & Youth Rehabilitation (MOSALVY)

For the home study, is it required for the applicant living overseas in Cambodia, or for the sponsors living in Canada, or both?
How do we go about getting a letter of no objection issued by the Ontario Ministry of Community and Social Services.
How do we get the approval letter issued by the Council of Ministers in Cambodia, and what are the requirements?
And finally, we would rather have the adoption process done here in Canada rather than in Cambodia. What is required for this and is 4)Adoption certification issued by MOSALVY required.

Thanks for your help. This part of the process has me stumped.