There are many thousands of apple tree varieties (7500+)
Apple trees can live for more than 30 years
Apple trees fruit better if they are pollinated from another variety (two more varieties for some apples).
Trees need a balance of roots, new wood and leaves to perform well on fruit production.
Most trees are grafted on to a special stock (not grown from pips). This determines the size of the tree.
So how to use this Information
Think about the apple(s) you want and the conditions in your garden. Match your choice from information about specific varieties. Soil conditions geographic location and other knowledge is available from specialists, a quality nursery or the RHS fruit group.
Buy with care bearing in mind the tree is their to last. Give it space and appropriate soil conditions as the tree will want air and light as well as sustenance.
Pruning stimulates new growth, do it between winter to early March. Train tree to shape before serious pruning and do not over prune in any one year.
Other Commonsense Comments
Apples can be grown in pots. Choose a large one that will be stable and hold moisture and feed weekly from July to September.
Protect the roots of pot grown apples from drying out caused by sunshine on the pot.
I am not keen on the use of chemical ‘icides on fruit but rely on a clean environment and early removal of problems. I will add sulphate of ammonia to increase vigour or potash to help fruit production.
When staking a tree ensure the trunk isn’t damaged or rubbed.
Apples can be stored for 4-6 months and should be left on the tree as long as possible ie November in many cases
Apples are ripe when the pips have turned black and should come off the tree with a gentle twist.