The concept of terraforming Venus within 100 years sounds impossible with current technology and scientific understanding, as Venus' environment is extremely harsh with surface temperatures of over 460 degrees Celsius, atmospheric pressure over 90 times that of Earth's, and thick layers of clouds composed of sulfuric acid. But, here's a hypothetical plan using advanced technologies that might develop in the future.

Step 1: Shielding Venus

The first challenge would be Venus' dense atmosphere. To combat this, a large solar shade could be installed at the Solar-Venus L1 Lagrange Point to block some of the incoming sunlight. This shade could slowly cool the planet, reducing the extreme temperature.

Step 2: Locking Up the Existing Atmosphere

Once the temperature has been lowered, the next steps will involve dealing with the existing dense, CO2-rich atmosphere. Hydrogen or water could be imported to react with the CO2 via the process known as the Bosch reaction, which yield reads of carbon (graphite) and water. This would reduce the atmospheric pressure and produce needed water.

Step 3: Magnetic Field Generation

Venus does not have a significant magnetic field, leaving it without protection from solar radiation. Humans could construct planet-encircling superconducting cables to artificially generate a planetary magnetic field.

Step 4: Formation of Oceans and Continents

The graphite produced through the Bosch reaction and the water could hypothetically form the beginnings of new land and oceans.

Step 5: Introduction of Life

Microorganisms specially engineered for the new Venusian climate could be introduced to convert the atmospheric nitrogen and remaining carbon dioxide into oxygen.

This endeavor is daunting and would require many technological and scientific advancements. It also presents numerous ethical questions, such as the potential destruction of any indigenous Venusian life forms. Furthermore, the entire process might take much longer than 100 years.