The logins for the two forums are entirely separate, so if you can’t login to the old forum it’s mostly because you’ve mis-remembered the either/both the username and password. There is no plan to unite accounts in each forum as part of the move is to slough off old moribund accounts. If you need a password reset for the old forum, use the controls on that forum.
In the old forum, you are not required to login in order to read the old forum. So, unless you want to post there I’d not worry unduly about the login (I’ve just tested - logged out of my account and could still search). However, we’d much prefer you post here as the old forum will probably be closed (at least for posting) if this forum works out.
I’m not sure about the forum posting rate. I guess this is an anti-spam default setting. It can possibly be altered or may go once there are a few more posts.
I’ll make a new post re Stamps - see here. I’ll also put this in the meta category of the forum.