Step 1 of terraforming Venus is to freeze the entire atmosphere, which only takes 70 years the sun shade is built
Simple one-dimensional models suggest about 200 years to cool off Venus's atmosphere, neglecting heat from the crust. Birch was at least good enough to cover the heat releases of phase transitions of the atmosphere. I haven't found other estimates detailed to that level.
Not every system, just the ones that are on the map. There's plenty of star systems in between the listed ones that aren't habitable for whatever reason.
Yep. The Inner Sphere's map only shows habitable systems. A 1,000 light-year sphere of stars around Terra would have about 2,000,000 stars.
However, Prosperina has a point: Projects Lowell and Aphrodite became white elephants as soon as Project Deimos succeeded. It was a lot easier to settle extrasolar habitable planets than continue terraforming Venus and Mars. Only massive lobbying kept the terraforming industry alive until it found a use for itself among the stars.
Mars had more water, for it's size than Earth did, until eons of solar-wind broke down the water molecules.
As of 2022, estimates of archaic Mars' water coverage indicate that there was enough water to cover Mars to a depth of 300 meters, which equals 43,000,000 cubic kilometers of water. In comparison, Earth's 1,386,000,000 cubic kilometers of oceans would cover its surface to a depth of 2,700 meters. Hence, proportional to its size, modern Earth has 9x as much water as archaic Mars.
On an absolute basis, archaic Mars had 3% of modern Earth's free water volume.
Soooooo The Star League learned not to terraform, from any/ all example in the Sol System?
In fact, the Terran system's terraforming industry was a powerful lobby and was involved in modifying many of the "habitable" planets found in the Inner Sphere. The old House Sourcebooks show how ecologies were commonly edited on a huge scale, leaving less than 50% of native life in place on many planets. The Terran Hegemony used terraforming on numerous worlds within its cramped borders to buy domestic political peace, with results ranging from Riken Minor to New Dallas, Brownsville, and Inglesmond. However, none of those efforts were as extensive as Mars and Venus.