Why do supervisors hide my rights from me?
I don't know your institution, but it's fairly likely that the right of appeal is limited to a subset of things like:


administrative irregularities and errors (e.g. you should have passed, but the examiners ticked the wrong box).
Immediate mitigating circumstances (e.g. your parent died the night before so you couldn't present a coherent defence of your thesis)
Inherent bias (e.g. you turned up in your favourite Everton shirt and know the the examiner failed you because he's a Liverpool fan)


The precise topics should be documented (properly, on paper) in regulations available from your registry (or however your individual institution labels that service).

In particular, it almost never covers academic decisions, or problems arising from previous poor supervision advice, which is typically meant to be dealt with far earlier in the process when it first arose.