Can atoms with top / bottom quarks exist? Do we have examples in nature or the lab of atoms constructed of 2 top and 1 bottom quark and a tau selectron?
How would its properties differ from a hydrogen atom?
 A: this question is really severely damaged: the title (top/bottom quarks) does not match the question being asked (up/down quarks plus tau electrons), and the question literally being asked has a meaningful typo (tau selectrons) which invokes ideas from the still-speculative physics of supersymmetry, which is even crazier.
To answer the question you literally asked:
Stau bosons
We do not have experimental evidence at all for any supersymmetric particles, to my knowledge: so of course we do not have experimental evidence that one has ever orbited a proton. Furthermore, we do not know if the stau (the "tau selectron") is the LSP (lightest superpartner) or whether there is even a conservation law (of the so-called "R parity") protecting superpartners such that it would even be stable over a long enough time to "orbit" a proton.
Stau chemistry would have a lot of differences from electron chemistry; in fact in the preceding sentence "orbit" is in scare quotes because the stau is almost certainly so massive that we would think of the proton as orbiting the stau rather than the other way around. It would be interesting to know if you could indeed confine two stau particles together in the same quantum state by using an orbiting $\text{He}^{2+}$ nucleus; the stau particles would have no strong force compelling them to "stick together" the way that protons do. If you could, then the chemistry would actually be much richer, as there would be a difference between, say, Helium nuclei orbiting the 2-stau core and two protons orbiting the 2-stau core; one could tentatively guess that in the latter case the protons would probably separate the 2-stau system into two 1-stau systems, so maybe the staus would be confined if $\text{He}^{2+}$ occupies the S-orbital but not if protons do. They have the capacity, as bosons, to all occupy the same state, but they do not have the attractive force, as hadrons do, to actually desire to do so.
If you could get multiple protons orbiting a "stau nucleus" then it would look a lot like a backwards periodic table, as the structure of the periodic table comes from the quantum mechanics of spherically-symmetric central-force potentials. On the flip side you'd have a very rich theory where, say, a 10-stau nucleus has 5 protons filling up some energy levels but also 5 $\text{Li}^+$ ions filling up the same levels (since they're different fermions and can do that), with 2 electrons each orbiting those $\text{Li}^+$ ions, a really strange set of 3-body systems. But since the nucleus doesn't have a force to draw it together I can't really imagine that the system would rather Bose-condense than simply scatter into 5 "normal" stau-proton orbits and 5 "weird" stau-lithium orbits. 
A tau lepton orbiting a proton
Since the tau lepton has nearly twice the mass of the proton, these would have to orbit a common center-of-mass. This means that the quantum mechanics can probably be analyzed for this particular system, but will rapidly explode in complexity if we put another tau particle in "orbit" around an $\text{He}^{2+}$ nucleus.
However none of this matters because the tau will decay into something else (usually hadrons, most often a $\pi^-$ and $\pi^0$) in $10^{-13}\text{ seconds},$ before any meaningful chemistry can be done; the $\pi^-$ will then rapidly become a $\mu^-$ which rapidly becomes an $e^-$. All of these reactions involve other particles which can easily kick the remaining particles "out of orbit", so only if you're really lucky would it settle down to be an $H$ atom rather than an $H^+$ ion.
If you're really lucky the orbits of the two particles are so fast that you get a relativistic time lengthening of their lifetimes, but it seems unlikely that it would span enough orders of magnitude to make this sort of thing observable.
Top/bottom baryons
Top quarks decay too fast to form hadrons. Bottom quarks have been observed both in meson and baryon forms, but decay really rapidly, as with the tau electron.
A: According to Wikipedia the predicted top quark lifetime of $5 \cdot 10^{-25}$ seconds is too short to attract other quarks to form a baryon, let alone find an object to orbit to form an atom.  Various charmed and bottom baryons have been observed, but no top ones.
