Just going off the top of my head, so this might need a few corrections, but...
If you're trying to reverse aging, you're probably interested in telomere repair, telomeres basically being the little safety caps at the end of DNA strands that keeps them from unraveling when they duplicate. However, after every DNA duplication, these telomeres degrade slightly due to how DNA duplicates itself. Some cancers are already very capable of fixing their telomeres (i.e. HeLa cells are kind of immortal), however, cancer is not very successful at keeping you alive. And even if you could repair your telomeres indefinitely, there's still that general breakdown of DNA as mutations accumulate over your lifetime. After awhile your DNA kind of fails at doing its job, cancer would likely accumulate, you die.
As far as viruses go, I'm fairly sure they don't alter your entire DNA, but rather a small section of it. This is fine for the virus cause it doesn't really need to alter your entire DNA to get your cell to replicate it. However, due to the build up of mutations and the gradual breakdown of telomeres in your DNA over your lifetime, I don't see how using viruses to 'replace' your DNA would be feasible unless it did a complete replacement. I'm sure someone's looked into it, but I haven't heard any breaking stories on that yet.
Personally, I'd be a little more interested in mechanisms like Mismatch Repair that your body already uses to repair your DNA when it mutates.
For cloning.. just cause you clone someone doesn't mean their clone is the same as them.. Even with the same DNA, two people raised in different environments can develop different skillsets, personalities, you name it. Plus, you're really bottlenecking your entire gene pool. Without that diversity, just one well mutated disease could knock the whole population out.
No comment on the bionics bit, since I've never really studied up on prosthetics. I kind of like my limbs the way they are though lol
If you're still curious, I'd recommend you to PubMed or Google Scholar for further reading.
Cheers