"after 9 o'clock" is 九点后. It can be 9:01 or 11:00

For example, If you go to a restaurant at 10:05 you could be told 九点后不供应酒精饮料 (No alcoholic beverages served after nine o'clock)

"九点多" means little later than 9:00 but not past 9:30 which is "九点 半" and definitely not past 10:00

九点左右 (around 9:00) could be 8:55 or 9:05 (not past 9:30)

"after 9 o'clock" is 九点后. It can be 9:01 or 11:00 and even later

For example, If you go to a restaurant at 10:05 you could be told 九点后不供应酒精饮料 (No alcoholic beverages served after nine o'clock)

"九点多" means little later than 9:00 but not past 9:30 which is "九点 半" and definitely not past 10:00

九点左右 (around 9:00) could be 8:55 or 9:05 (not past 9:30)