Pension

It’s usually restricted until pension age - 55. Call them and ask

Why would you want to?

That would be a mistake. If you mange to do it (most that say they can is an actual scam) would come with huge charges (up to 55%). You lose out on compound growth (you lock in loses) and restricts your future tax-relieved contributions to a much lower limit (e.g., £10,000 per year) rather than the standard annual allowance.
Unless you are terminally ill, you should forgot the money exists.

You can but you get taxed loads on it so will lose a chunk of it