Need help with entity tagging
But what about new entities (movie or production company name) that
  trained system hasn't seen how can we tag them. Re-training the model
  every time with new released movies won't be feasible.


A NER model should not have to be retrained to tag a new text it has not seen before. If trained successfully it will use information it learned from the labeled data and be able to apply it on new data. For your use case this could be information such as:


Capitalization - common for movie titles and production company names
Words used - frequently used words for either movie titles or company names
Where in text - movie titles perhaps appear early in texts


spaCy is a good library to get started with NER. Here is an example on how to train one using your own data.