Nothing
They can do both, but it is up to them to decrease usage of fuels in order to increase planet temperature.
Increase Due to melting polar caps
Global warming
If you decrease a planet's orbital radius, its surface temperature will increase.
Is our increase in population good or bad for the planet
The mass of the black hole would increase in proportion to the mass of the planet
No, your age would not increase. The rate at which you age would increase, but not your actual age. You don't travel into the future just by traveling to a different planet.
None exactly ... the closest is Jupiter at 230% increase.
If you increase the albedo, more solar radiation will be reflected back into space and so the temperature will be lowered.
As a general rule, the surface temp will go down and the length of the planet's "year" will increase the farther it is from the sun. There are exceptions, but that is the general rule.
To increase gravity, you would need to increase the mass of the object or planet exerting the gravitational force. To decrease gravity, you would need to reduce the mass of the object or planet exerting the gravitational force. Another way to decrease gravity is by increasing the distance between the objects experiencing the gravitational force.
In 2006, because of the rapid increase in "planet" discoveries, the International Astronomical Union re-defined the term "planet". The 2005 discovery of the Kuiper Belt Object called "Makemake" was therefore a "dwarf planet" rather than a real planet.