Can the object of a preposition be the subject of the sentence? Please Explain.?

Answer 1

No. However, there are a few cases where the verb agrees with the object of the preposition, if that's what you're asking about. 

Some of the sugar is on the table. (Subject: Some. Verb: is. 

Some of the boys are in the house. Subject: Boys. Verb: are - agrees with "boys".

Does that answer your question? "Boys" is NOT the subject in the second sentence, but the verb agrees with it. 

Answer 2

Well, the object of a preposition is in objective case and, being the 'object' can't be the 'subject.'