How does the length of an individual's telomeres compare with the length of the telomeres of an older individual of the same species? How does it compare with the length of telomeres of an older individual of a different species?

The telomeres of one individual will be longer than the telomeres of an older individual. The length of telomeres is different with every species, so the differences of length is undetermined until the speciation of the older individual is specified.