We use nightly IRIS backups which are moved to a network share, so Test can restore the backups to an alternate application data DB via a script.  We always have 2 application DBs defined, so we can script a restore on a weekly basis so the data is readily available if a developer needs it - they simply swap from the active data DB to the alternate (the alternate is always the target of the automated restore so as not to interrupt any data depending testing which may be actively going on at the time of restore).  

We have found this to be very effective for our needs for multiple internal applications. 

if you are wanting to completely render the page within the context of another page, then using <iframe src="package.page.csp" </iframe> is going to be your best bet.  Remember that a csp page isn't just a static HTML snippet - it is an entire renderable page, along with pre-page headers, etc.  That is why OnPreHttp(), OnBody() and OnPostHttp() are all included in the page framework for a .csp.  If you simply want to show what is 'rendered' when you call the page directly, you can play with calling OnPage() (which contains the compiled version of the entire body of your .csp file), but that may not operate correctly when called in isolation - it is intended to be called as part of a full pageload process, which the iframe approach above would provide.

It's been a while since I had to look these up.  You probably have to select the option for 'show generated code' order to find it.  Unless you overwrote the default package, they should show up as csp.****.cls classes (in the "csp" package)

the .csp file compiles into a subclass of type %CSP.Page.  When it is called, on the back end the various methods of the subclass of %CSP.Page are involved in order to stream the content of the .csp page.  Please see the documentation link above for more details.