I heard of file called vold.fstab in /etc..can modifying that be of any help??i want to be able to remount as a common user.
Or is it possible to give specific permission to just run remount command as user??like is there a setting where certain command access can be set to particular users other than just root user??
No. It is not possible unless you install a custom android build which, for all practical purposes, lacks a security model - or use a local privilege escalation attack to obtain a temporary root shell to issue commands from.
Even if you were to let non-root users remount the filesystem, they wouldn't be able to actually change much of anything on it as they would lack the necessary file/directory permissions, so literally fulfilling your question would be pointless.
Likely what you want to do is install an at least somewhat secured tool for obtaining a root shell when needed - ie, "root" your phone. That would let you both remount the filesystem, and make changes to it, but would hopefully prevent/discourage other random code on your device from doing so.