Just to be clear, I already read the indexing documentation help page. I still have a question. I published my game around 6 times on this site, every time I add a few scenes with around 500 renders (It's a 3DCG game). Every update adds 50-100 mb of content. They also extend the storyline of the game significantly. My questions are, 

1- Is it proper for me to post every update as a Major Update?   

2- I noticed that when I do post every update as a Major update, the views/downloads rise up quickly for a day or two, then get back to their normal ranges after that, but sometimes after one or two days from the downfall, they get rise up again for a day of two. Why does this happen? And why doesn't it happen every time? 

Games only get a temporary boost from major updates, so that other games get a chance to be on top for a while. I don't think there's a special reason why it doesn't always work, just lots of new and updated games all the time, competing for search results. And I think it's okay to announce a major update every time if they really are major.