I think the most standard classic Mega Man game that covers everything and does not have a weird amount of extras or difficulty would be Mega Man 2. 2 and 3 are the best of the original series. Most are okay until you reach the Dr Wiley levels then the challenge rises a lot. Skip 7 and 8...
Not really, mostly from there not being many left around to have issues. Their forum community was a lot more extreme than anything here but that was around 2012ish. Their site went down a few times, once was for a few months which had almost everyone leaving. Then they reset their forums and...
Their forum was not doing so well around the time of the merger and a lot of them left anyway. It was only a small few that stuck around for the community stuff. Their main site team did stick around but they never really do much forum stuff.
A completely new crew takes care of the front page now since the merger so I honestly have no idea what their criteria is anymore. I have never really looked into it at all since the front page stuff was handled by the ZI staff and I was last in a ZI chat in 2012.