Hi, Ankita, and thanks so much for your question! We're so glad you enjoy the forum!
As for what park you can go to when you arrive, the answer is any of them! All of the theme parks will still be open when you arrive at 2:15, but the best thing to do to get the most amount of time is to check which park is having the evening extra magic hours. The Magic Kingdom and EPCOT are typically the parks that are open the latest, and if you add up to three hours of evening extra magic hours, you can really get a full day in either of those parks if you stay until the end of the night!
If you prefer to take it a bit easier that first night so you can head out first thing in the morning, you might try Disney's Animal Kingdom or Disney's Hollywood Studios. Traditionally, those parks are not open as late in the evening as the other two, but you can still enjoy several hours if you arrive around 3 o'clock.
You don't say when you are arriving, so I can't check park hours for you, but you can go to
www.disneyworld.com to see which parks are open until what time. That might help you decide!