Can UHT milk be chilled/ frozen?

Yes, UHT milk can be chilled. You can also freeze and unfreeze UHT milk, but the texture and flavour of milk may vary. 

Due to its naturally increased shelf-life, it does not need to be refrigerated until opened. Because UHT milk does not require boiling before consumption, chilled UHT milk can directly be used in milkshakes, smoothies, fruit bowls, cereals, post-working drinks and many more.