Q.Blackthorn tree
Given as a gift, but I have a very small garden. Can I grow this bush/tree in a tub? Also, would I be able to contain the size by pruning?

My research shows that this bush would be best grown in the ground and would not do well in a container.
Keeping the size contained to 6 to 8 feet with pruning is possible and will result in a manageable specimen.
https://www.gardeningknowhow.com/ornamental/trees/blackthorn/growing-a-blackthorn-tree.htm