I believe it is possible for one to understand both or more religions. Unfortunately there are many conflicting beliefs and this is where the issue comes about if one can truly practice both. If one wants to be a wonderful human being (for example I believe you are from what I read from your posts) one can perhaps live with understandings that don't conflict and put away conflicting beliefs. Would it create practical happy and healthy life, I don't know?
I like the beautiful line you have in your profile as,
Pave to Musalman, pave Hindu, Sikh ve, sada ve Rabb jive, ek sada dil ve. Apne aap nu tu vakhra kyun samjhe...?
I read the above as, " You may be Muslim, a Hindu or a Sikh I too wish my God to exist, I too have a heart. Why you believe you are different".
If you created it yourself even more kudos to you.
Any errors in the above I stand corrected.
There is a wonderful Shabad in Sri Guru Granth Sahib which I refer to often and I refer below in case you missed it. It is written Bhagat Kabir (by birth Hindu) and is in our SGGS.
The answer is NO. And there is nothing to discuss, though one can ramble. The Sikh Rehat Maryada states as follows:
The Definition of Sikh
Any human being who faithfully believes in
(i) One Immortal Being,
(ii) Ten Gurus, from Guru Nanak Dev to Guru Gobind Singh,
(iii) The Guru Granth Sahib,
(iv) The utterances and teachings of the ten Gurus and
(v) the baptism bequeathed by the tenth Guru, and who does not owe allegiance to any other religion, is a Sikh.
The thread is closed in order to prevent philosophizing on this point.
Thanks to Ambarsaria ji for his sensitive contribution in explaining the conceptual problems.