Cloning Body Parts: It used to be done, but in the current era is obsolete twice over; first, replaced by organ printing tech (basically, 3D printers for organs), and second, by healing vats and having things built by medichines in situ. Hospitals and clinics probably have some organ printers lying around for special cases, but revolutionary as it was when it was first developed, organ cloning is now strictly for museums.
Clone by Conversion: It’s possible, with the right abominations of technology (basically, start with a healing vat and a cerebral bridge, then add evil) – but since you’re just using the original person as organic raw material, the applications are sharply limited. Basically, if you need reinforcements and have the equipment such that this looks like a reasonable way to go, bear in mind that you can get to exactly the same place in the end by popping along to your friendly local butcher and explaining that you’re buying meat for a family pig roast.
In many cases, this also avoids the ensuring war crimes trial, which is often a point in its favor.
(There is also the technique used by… certain intelligence agencies of covertly implanting sleeper agents with a Trojan device that permits an agent or an intel AI to be remotely downloaded into their brain, overwriting their original mind-state. But decent people shouldn’t think about such things.)
In its simplest form, where you’re just using cloning technology to replicate military-grade bodies as quickly as you can, it may be valuable. It won’t help you with absolute growth rates, since the expensive part is growing the minds to put in the bodies which is much harder to rush, but if you have noetic backup technology at least you can get your casualties back into the field faster.
If you are actually attempting to run what is functionally a non-divergent fork army, however, this will fail dramatically as soon as anyone notices – because, gee, do you think having your entire army react in the same way to every situation and stimulus might just open up a few security holes?
If you’re really lucky, this won’t get everyone killed.
Artificial Limbs: Quite possible, but a disfavored technology in Imperial society; in the modern era, when biotechnology is also advanced, it tends to be preferred for internal solutions, or at the least it should be used to ensure that the bionic technology is well integrated with the meat: bones reinforced with carbon fiber, muscles interwoven with myomar, a skin supplemented with a layer of armor gel, and a well-concealed mass driver hidden mostly within the flesh are much more likely than simply chopping off a perfectly good arm and replacing it with a mechanical prosthetic one.
(And, of course, cloned grafts are the way biotech solves the pure replacement issue.)
(I thought I’d do my trope-a-day to match the Blogging from A to Z letters, too, if you’re wondering. That way everyone gets double the pleasure, double the fun… or at least double the posts.)
Belly Buttonless: Averted. Of course clones have them. How did you think they got their nutrition in the exowomb/cloning vat?
(Bioroids, now, they don’t have them because they’re assembled from the equivalent of 3D-printed organs on a framework, not grown as a single organism. But they’re meat robots, not any kind of natural being.)
Adam and Eve Plot: The colonization of Valiár (Thirteen Colonies), in which the catastrophic failure that destroyed the majority of the colonists in cryostasis aboard the Swiftrunner left a first-in team half-a-dozen strong as the only people around – and it’s not like in subluminal colonization you get to turn around and go home. You colonize or you die.
Subverted inasmuch as they knew perfectly well that their genetic pool was in no way up to the job, even for such fine examples of genefixed Eldrae anthalis as they were. As such, after maximizing the genetic diversity that was available, it was time to send in the clones ; and Valiár today remains almost entirely populated by serially cloned descendants of the original set of archetypes.
 Yes, they could handle this differently NOW, but they could not THEN, and NOW NOW is based on THEN THEN.
DISCLAIMER: All population figures found herewithin should be considered provisional and contested.
Ongoing controversies exist where the correct measurement of population figures is concerned, including:
Accounting of clone families;
Accounting of fork families, both synchronized (cikrieth) and desynchronized, and the measurement of repeated non-persistent forks;
Accounting of group intellects, including both true hive-mind species (such as the hjera and cusaron) and independent Fusions, representing single minds in a multiplicity of bodies, and collective consciousnesses (such as the Eldraeic Transcend), representing multiple independent minds sharing only specific layers; as well as multiple intermediate and overlapping cases;
Accounting of collegiate-intelligence species, such as the embatil and aklaknak;
Accounting of naturally fork/merge capable species, such as the codramaju;
Accounting of biologically casted species in which only a single caste or a subset of castes is sophont, such as the vlcefc, or the gender-based equivalent;
Accounting of polysapic species possessing multiple natural minds acting in accord, such as the múrast and voctonari;
Accounting for members of species not possessing sophoncy at all points during their lifespan, including but not limited to the majority of r-selected species;
Accounting for presently-inactivate species members, including those in long-term cryostasis/nanostasis or data storage;
Accounting for the deceased retaining active cognition within technologically-mediated afterlives;
Accounting for unconventional forms of identity, such as teleological threads;
Location accounting of infomorphs (by processor or by avatar/point-of-interaction location);
Legal differences of opinion on the prosophont/sophont boundary;
Calibration of population accounting for post-sophont entities, both regarding the appropriateness of categorizing such minds on an equivalent scale with baselines, and inasmuch as high post-sophont minds are capable of generating transient and/or lasting sophont memes in the normal course of cognition;
And so forth.
While recognizing that in many cases appropriate answers to these questions is determined contextually (the computation of required life-support capacity obviously is dependent on bioshell-population, for example), the meaning of population in the generalized sense requires the resolution of these questions, many of which are hotly debated philosophical, theological, and/or political topics in many of the Worlds’ polities.
As such, we have chosen to use population figures, in all cases superseding those locally provided, established by the Imperial Grand Survey, whose methodology has the virtue of being consistent, transparent, and well-documented (see publication IGS-1134/P rev. 112).
– from the preface to the Associated Worlds Factbook, Conclave Press