By definition Pi is the ratio of a circle's circumference to diameter. Because a numerical calculation always results in a never-ending decimal number, one can keep calculating the numerical value of Pi with infinite number of decimals. As for what practical application needs to know Pi's value with one billion decimal accuracy, the answer is none
At what decimal place does it become inaccurate on Earth due to the slight gravitational warping of our local space?
Common issue with text editors on Windows. They usually don't do memory mapping. It wasn't possible in old Windows versions and thus most software ignores this and instead tries to load the entire file into RAM. Most editors on Unix-like systems use the mmap POSIX API to map files into RAM, and thus instantly load files of any size.
I wrote a quick program to find out how many occurrences of '1337' exist in pi to 1 billion digits. The answer is 100393. The average for a number of this size would be 100010 which proves that pi (to 1 billion) places is a slightly more leet number than average.