stopped by/at

1a. Some friends stopped by our house for a chat.
1b. Some friends stopped at our house for a chat.
2a. Why don’t you come by my place later?
2b. Why don’t you come to my place later?
3a. She succeeded by pure hard work.
3b. She succeeded due to pure hard work.
3c. She succeeded because of pure hard work.
Please correct the above and comment.

No corrections are necessary.