Sure is a lot to earn (and I am always learning).
Anyway, you are at least making the effort, if just as a passing interest.
To briefly answer some of your questions.
> "Why do you think that Venus is so hot when it is so far from Sol?"
Because according to the hypothesis, Venus was ejected from Jupiter under violent conditions and went sunwards on a very extended ellipsoidal orbit.
On several occasions Venus approached very close to the sun and became incandescent.
Venus also had several close encounters with Jupiter during this phase on its return trip.
Around 1500 BC, Venus (ie the cometary-looking protoplanet) had two encounters with the Earth, 52 years apart, with discharges of potentials resulting in a thermal effect caused by change of momentum into heat.
Later in the first millenium BC, Venus also encountered Mars several times in similar fashion and with similar effects.
The thick atmosphere (remnants of its once cometary tail), which is virtually shielded from the sun (today, only 2% of the sun's radiation reaches the surface), keeps the core and surface heat intact.
> "Why does Venus have 'no' magnetic field?"
If Venus is very hot at its core as is theorized, perhaps more than 1500 degs F, then iron will austenize and austinitic iron possesses no magnetic properties.
Anyway, I differ from the accepted dynamo theory of magnetic field generation.
> "Do you have any theories as to why Venus spins in the opposite direction?"
One theory purports a for a method of ejection from Jupiter (or Saturn, as some say).
This is basically a "fissioning" event.
The other theory claims that the anomalous retrograde axial rotation might be due to the sum totals of all these encounters mentioned above.
Whichever way is correct, both are catastrophic.
> "Do you have any ideas as to why Mercury's orbit is retrograde?"
I do know that Mercury spins on its axis three times, while the planet orbits the sun twice.
This is the anomalous 3:2 resonance.
Still unexplained today.
However in earlier times Mercury, the "winged messenger", might have been responsible for the fall of the Tower of Babylon (amongst other catastrophes), when the planet quickly passed by the Earth, causing devastation in many localized areas.
Purely hypotheses I know, but nevertheless quite fascinating stuff don't you think?