Questions on SharePoint Inline

Hi Community, 

One of our customer raised the below query:

They're looking for the best practices to achieve the below things in SPO. 

• Set data uploaded to set document library
• Enforcing a naming convention when creating folders in a library
• Require certain metadata on upload
• One drive checking out documents
• Approval for document changes process
• Can discard file changes when checking back i
• What settings are available to set when a major and minor version created
• Can we limit minor versions to document owners
• If we delete a version does the versioning numbers remain the same so if we delete 1.1 will we still see 1.0 and 1.2
• Personalized rankings on search
• Best practice of items in a doc library
• Is it better to have loads of sites with small amount of doc library or one site loads of doc library
• Current limits on doc library
• Resource allocation

Any points would be of great help.

Many thanks in advance.