I see the 14th amendment as a goal we are still striving towards. The 14th amendment states that all persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. It is, in basic terms, to fight against racial injustice, by saying that all people born naturally as a US citizen has all rights of an US citizen. Therefore, it is fighting against, and is not a failure in terms of unity against racism.
The 15th amendment was successful in that it put out a firm barrier, in terms of legislature, towards banning a person’s rights based on skin color.
I don’t quite understand the third question. However, I do know that convict leasing was a form of slavery, or servitude, when prisoners in the southern states were purposely lead to work in private railroad, mining, etc. companies.