In 1, "surprise" is being used as an adjective to describe "party."
In 2, yes, all the terms are similar, but watch the spelling -- "stadium"! I wouldn't use "baseball ground," though. Maybe others would, but I've never heard that before.
1. Let's throw a surprise party for Henry.
[What is the part of speech of 'surprise' in this sentence? A noun or an adjective?]
2. baseball field, baseball ground, baseball steadium, ballpark
[Are they all the same in meaning? Which ones are frequently used?]
3 answers
2. baseball field, baseball ground, baseball stadium, ballpark
[Okay. Thank you!]
[Okay. Thank you!]
Here's a slight difference for you.
On Sunday, my family and I are going to the baseball stadium in Houston. (The stadium includes the whole building that surrounds the actual field, in which there are the spectators' seats, the restaurants, the shops, etc.)
The Astros will be playing baseball on the field (the green grassy field with lines and bases on it) at Minute Maid Park: https://en.wikipedia.org/wiki/Minute_Maid_Park
Again, I've never heard anyone refer to a baseball ground.
On Sunday, my family and I are going to the baseball stadium in Houston. (The stadium includes the whole building that surrounds the actual field, in which there are the spectators' seats, the restaurants, the shops, etc.)
The Astros will be playing baseball on the field (the green grassy field with lines and bases on it) at Minute Maid Park: https://en.wikipedia.org/wiki/Minute_Maid_Park
Again, I've never heard anyone refer to a baseball ground.