i can see a few years being shaved off, and in districts of some countries the local administration would not be entirely accurate. but not 20, you wouldn't expect to get away with it, and unless you'd been grown in a lab with superhuman cellular structure, i don't believe you'd get away with it.
i cant really see that you'd lie that you are 20+ years younger, and it would be pretty obvious on the training pitch (and physio table, where he'd spend most his time), so going to give the benefit of the doubt.