Q.Do Lemon Trees normally Have Long Thorns on Them?
Mine has long thorns and you can’t reach inside the tree to pick fruit without getting stuck.

Certified GKH Gardening Expert
Yes, this is normal. All citrus trees have thorns. You should only be worried and remove a branch if it appears that it is a rootstock sucker. If there is a branch that is significantly thornier than the others, it may indicate that the rootstock is trying to produce branches. Typically, branches from the rootstock will grow from the base and if you look carefully, you will see that the branch actually starts below the graft line. Rootstock suckers like this should be removed.

Most all citrus trees you buy today are grafted onto a hearty disease resistant rootstock. Most of the rootstock is sour orange tree stock which are highly resistant to diseases. This means you'll get a better stronger producing tree without the worries of it sucumbing to a disease.
Even those that advertise lemon trees with little or few thorns, as these trees mature they will grow more and more thorns. Lemon trees are notorious for having a lot of thorns. Many thorns can grow as long as 6 inches on mature trees. This keeps the kids and animals from climbing up the trees.