Thanks for the questions Aditya!

1. If your question is whether the percent lift will be the same, it will not. Often the CUPED metric percent lift will be less extreme (positive or negative) than the original metric percent lift.

2. Theoretically this is possible, however this would only occur if your experiment data are negatively correlated with the pre-experiment data. If this is the case, you probably want to check for bugs and possibly lengthen the pre-experiment window.

Hope this helps.