Its called blossom and is likely caused by different pH levels in the soil..

More acidic will turn them blue/purple, more alkaline will turn them pink/red :)

Sir / Madam that's a Tree.

I think that's grafting. Two different trees grafted into what looks like one.

Not sure if this one is an example of grafting, I have seen normal trees (not grafted) do this on many occasions..

Not saying it isn't grafted, but I don't think it is - can't see sins of such on the trunk etc either...

A crape myrtle, if I am not mistaken.

Beautiful! I have a rose bush that does this. It has yellow and white roses!

Could be unintentional aswell. Lots of trees have a very sturdy root that is resistant to lots of pests and can survive in most conditions. On top of that they graft a pretty part that usually doesnt grow to tall. Sometimes though the root part grows partly through the top part of the tree and you get a result like this. To say for sure what it is you need to wait until they cut the tree again because the branches from the root part would be much larger than the intentionally grafted ones.