Is it possible to use Lucene as full fledged data store (like other(mongo,couch) nosql variants).
I know there are some limitations like newly updated documents by one
I've only worked with Solr, the Lucene derivative (and I would recommend using Solr to just about anyone) so my opinion may be a little biased but it should be possible to use Solr as a datastore yes, however it wouldn't be very useful without something more permanent in the background.
The problem you may encounter is that entering data into Solr does not guarantee you will get it back when you expect it. Baring the use of pretty strict faceting you may encounter problems retrieving your data simply because the indexer has decided to lump your results in a certain way.
I've experimented a little with this approach but the only real benefit I saw was in situations where you want the search index on the client side so that they can search quickly internally a then query the database for extended information.
My suggestion is to use solr for search and then have it return a short sample of the data you may want as well as an index for further querying in a traditional data store.
TL;DR: Yes, but I wouldn't recommend it.