Hi Dinesh,
I believe the best way to get started is to understand how OpenACS works. A few good resources for the OpenACS templating system can be found here:
(thanks to the relevant sources)
A Quick Intro to OpenACS Templating - Rubick
http://rubick.com/openacs/templating
OpenACS Templates Reuven - Lerner consulting
http://www.lerner.co.il/atf/atf_105
Jim explains OpenACS in an IRC session
http://jam.sessionsnet.org/files/download/templating-intro.txt?version%5fid=3168
Here you can find demo bits of code:
OpenACS docs - I found this doc really helpful adn feel it should be advertised more than it currently is.
https://openacs.org/doc/acs-templating/demo/
Here you can find the demo for creating a new OpenACS package:
Again OpenACS docs
https://openacs.org/doc/openacs-5-2/tutorial-newpackage.html
Here you can find how to turn your OpenACS package into a dotLRN package:
Forum posts, regards to Cathy and Nima for these two.
https://openacs.org/forums/message-view?message_id=198901
https://openacs.org/forums/message-view?message_id=299982
I had a similar problem to you in trying to find demos and tutorials that could get me started and I found these documents to all be very helpful. Hope they help.
Matthew