Retrieve the site collection using rest api

Yes it is possible.

Use REST api to retrieve the data from the list/library across the site collections. 

 https://blogs.msdn.microsoft.com/richard_dizeregas_blog/2013/04/01/cross-site-publishing-alternatives-in-sharepoint-onlineoffice-365/ 

 

You may also consider search approach which is called cross site publishing, enable document library as a catalog. Use content search webpart to render the items. 

https://technet.microsoft.com/en-us/library/jj635883.aspx

https://technet.microsoft.com/en-us/library/jj656774.aspx#BKMK_Share_library_list_as_catalog