To verify the data table, three identical tables are created. Then the check sum is checked between the tables?
No, you look for two identical.
When writing 3 times, if a power fail occur, the two identical dati will be correct, although possibly one issue too old. The possibility of picking up one issue too old is rarely dangerous and a whole lot better than working with bad data.

If the EEprom memory is used only for reading can a lost of data occur? How do you write it?

Erik