Kasim was being pushed along by the crowd.
Yes, this is a passive-voice clause. "Kasim" is the subject, "was being pushed" is the predicating phrase, and both "along" and "by the crowd" are adjuncts in the predicate.
Subject and object are grammatical roles. There are also semantic roles involved in this sentence. "Kasim" is the patient. "The crowd" is the agent. Having separate labels for grammatical and semantic roles makes discussing these transformations and relationships much easier and simpler.
The crowd was pushing Kasim along.
This is an active-voice clause. Here, "the crowd" remains the agent, "Kasim" remains the patient, but the grammatical roles have changed. "The crowd" is the subject and "Kasim" is the direct object.
Sheena had been hit by a stray football in the playground.
Again, we have a passive-voice clause. The subject "Sheena" is a patient. The object "a stray football" is an agent. However, this isn't a direct object. It's not an argument of the predicating phrase "has been hit". Instead, it's merely the object of the preposition "by". The same thing holds true in the first example, where the agent "the crowd" is a prepositional argument and merely part of an adjunct.
Active-voice paraphrasings are just as easy to find:
A stray football had hit Sheena in the playground.
A stray football in the playground had hit Sheena.
Some active voice clauses have two objects.
I gave John those books last year.
The subject "I" is the agent. The indirect object "John" is the recipient. The direct object "that book" is the patient. Either one of these two objects could be the subject of a passive-voice clause:
Those books were given to John last year.
John was given those books last year.
Notice that there is a direct object in that second passive-voice clause. Also notice that John remains the recipient, even though "John" is the indirect object of the active-voice clause, the object of a preposition in one of the passive-voice clauses, and the subject in the other passive-voice clause.