Okay, Your question surprised me a little at the beginning but i will try my best to answer your concern! I have studies World Religions. Which included Religion like Christianity, Judaism and Islam. Others were not considered religions, but more like ''Cults''
Hinduism and Sikhism are both Cults, and technically not religions because this is a group of people following other people, whom they consider God. I am not trying to be offensive.
Islam on the other hand is a religion. And please dint be mistaken, many people think that Islam was founded by Muhammed (Peace be upon Him), but the truth is that He was a messenger of God, the last messenger of Allah, who's ways Muslims follow. Because His character was the Holy Koran itself, and He never did anything other than what God commanded HIM. Islam was always there, and was not founded by Prophet Muhammad (Peace be Upon Him). Judaism and Christianity also come under Islam, but the thing is that the followers of Moses (Judaism) and Jesus (Christians) Named their religion after their messengers. But just like our final messenger, Koran is the final word of God. The improved version of Bible and Torah. because both of them were also the word of God.
Hinduism and Sikhism are very similar to one another, since they both have temples. But even these two differ in many ways.
Sikhism: founded by Guru Nanak was an ordinary man, but now after i went to their temple i realized that they were worship ping Him. Praying to Him. which just seemed very wrong. He was an explorer. Sikhism was not a religion before, but Guru Nanak''s deciles became known as Sikhs.
Hinduism: Claimed to be the oldest religion, but. truly it is the oldest CULT. IT is a CULT, because they dint have a clear concept of hell/ heaven/ death/ the unseen and even Their Gods. I am have been to a Hindu temple as well, and the Preist of the Hindu temple talked to us, with much passion. Hindus have 33 million God, approximately. Their concept of death includes reincarnation which in some cases may be proven but not accurately known. There have been many cases where people claim they are reborn, but the truth is once you die, you die!!! I am not being rude or offensive here, that is not my intention, i am just simply stating the facts.
Anyways, if you have more questions, please dont hesitate to ask me on my page.
Hope my answer helped