Welcome to the forum,
Hopefully someone will be able to correct me if I am wrong here.
1) You possibly would need a MYSQL database for an operation such as this (I am unsure of this)
1a) As AM uses text files as it's database, an extra field maybe for when the title was added might be a work around for this, but it would require extra coding.
2) It is pretty useless if you are mass importing a lot of games (My point of view, I am currently doing PS2 and importing 2,000 + roms)
3) I am not sure if there are themes that may possibly do this, using scripts but again I am not 100% certain
If you are only importing a few at a time, then it might be an ok feature but when you are starting out and importing hundreds or even thousands, then you are not going to see a lot in the long run to start with.
If it does require a database of some sort, I cannot see the creator of AM re writing the code just to include this feature, I think you are the only person whom has asked this question.
Regards
Mark