Resignation and Company Clearance :'(

In our company, we need to file our resignation and accommodate the 45-day notice. And I complied. I already tendered my resignation. As agreed upon, my last day should be next week. Supposedly, priority sa notice period is to turnover right? So I have been trying to do just that. Just yesterday, I was told to hasten my timeline and finish my tasks (scheduled ng October). I have been negotiating about the tasks because I really cannot guarantee to finish it especially since I have to process my clearance which ideally takes a week. That's why I really want to begin with the turnover. But they won't listen and even blatantly threatened me that if I don't deliver everything they were asking for, my manager won't sign my clearance. I have many people to set an appointment with after I get my manager's sign (unit head, HR, HR training, admin, finance, etc.). However, for them to meet me, my manager has to sign my clearance first.

So basically, my manager has threatened to hold my clearance until I finish everything she asks for. Is this possible? I really find it unfair since I've been doing my job really well, and I'm the only one who has been doing his job on time in the whole project team,but I'm the one being forced to finish everything instead of my teammates who are delayed.

This attitude of theirs is the reason why I resigned in the first place. If only they can have me go overtime everyday, they would do it. But if they're the one who screwed up, they just go on leave and pretend to be sick for over a week.