I acknowledge that check in is at 4pm, however, If I wanted to check in from 10:30 am is that possible? If so, whats the cost for early check in?

If you are a Marriott elite status member, you might be able to check in early

I was there really early around 9, they said they are not able to check me in, as there was no room available, but can store the baggage at no cost

It all depends on availability of the room. If it is available I doubt they would charge you extra.

I arrived early for my stay there, it was a Thursday and I was able to check in early at 12pm. If you are unable to check in early they will hold your bags for you. There was no extra charge but it was not planned in advance.