1) As at any other time, your employer needs to agree when within the year you can take your annual leave. You don't have an automatic right to take vacation days within the notice period - your employer can choose to pay you in lieu of earned leave.2) It would be difficult to argue discrimination as, from the description, it is not apparent on what basis you have been discriminated against. It would be unusual to bother, but your employer can investigate any suspected abuse of policy and/or institute disciplinary procedures at any point, including during the notice period. You are still entitled to a fair process and the best thing is to go along with the process for the few weeks until you leave. After you have left, you no longer need to have anything to do with it.