Q.Crab apple trees
Do I have to plant 2 crab apples and if so how far apart can they be.

Crabapples, however, are bred for their flowers. Some varieties are sterile and do not set fruit no matter what pollen is available, but the Adams crabapple is self-fertile. Adams crabapple flowers set fruit when they are pollinated by other flowers of the same tree.
Plant the Adams crabapple in full sun in well-drained, acidic loam soil, either as a specimen or in small groups.
https://www.gardeningknowhow.com/ornamental/trees/crabapple/flowering-crabapple-trees.htm