3 Unfortunately, no. That functionality isn't available from the out-of-the-box web services. The only option that might work is using the Search Web Service (I'm not familiar enough with it to know). This walkthrough describes how to add your own custom web services to the product.

As mentioned earlier the web application is an IIS Site, but site collection is a SharePoint object and you will not see this in IIS, it resides in web application. You can have n number of Site collection in a web application. Usually site collections are our team sites, Project sites etc. Sub site & Lists, libraries