Can I use "inspect" in this sentence instead of "control"?
The police controlled the crowd.
And also, can I use "control" in this sentence instead of "inspect"?
Police inspected the scene.
Are they synonyms or not?
No, in English those two words are very different in meaning. In some languages, control has a similar meaning to inspect, verify or check, but in English, control in this case only means to exercise control.
Means that they made the people do what they (the police) wanted them to do.
Means that they investigated the place.
As you see, the meaning is completely different. You could use one verb instead of the other, but the meaning would be completely different.
"Control" and "Inspect" are clearly not synonyms.
(Source: Cambridge Advanced Learner's Dictionary)
In your sentences control and inspect are clearly not interchangeable. The sentences are fine as they are.