Image files uploading

How can I delete file using file model and set the maximum size?

How can I build a form based upon a model user which has a relationship of oneToMany with a file model (images)?

Assuming both are AR models, to delete it you can do $file->delete(). Maximum size is about FileValidator. Form part is described here: http://www.yiiframework.com/doc-2.0/guide-input-tabular-input.html