1.) It can be very hard to add an older game of a series (the first game is by all means impossible to add AFAIK) since the GameDB shows the latest entries of a series first and won't let you scroll through the results.
2.) I'd guess about 70-80% of the time your search vanishes if you enter too much of the game name, the results pretty much always vanish if you're not fast enough with adding the game (I'd guess after about 5 seconds)
3.) Pretty much identical with 1.) - You can't seem to see search results in list form.