What is the Relationship between AKB48 and SKE48? Are they a few versions of a song, cause I have seen three different ones listed as "River".? Is there any age limit to join? Or age where they have to graduate by?
AKB48 = Akihabara/Tokyo based
SKE48 = Sakae/Nagoya based
NMB48 = Namba
SDN48 = Saturday night = 20+ members
They are the 'sister group' of AKB48 and consists of different girls. They have their own singles and stages. Sometimes, they do concerts with both AKB and SKE.
In addition, sometimes SKE48 members are a part of AKB48's singles as well (for promotion or due to election events).
SKE48 sometimes performs AKB48 singles during their stages or concerts.
The age limit to join depends on the particular auditions. I think the youngest ones are around 11 years old.
Graduations are a completely different story. A girl can graduate for a wide variety of reasons and doesn't necessarily have to age related.