Thanks for your bug report. Both of the issues you describe seem to be expected behaviour.
The first issue: when you connect to a server, mIRC will always cycle through the ports listed for that server or network in your servers list. If you have an entry in your servers list for that server or network, and you want the server to always use a specific port, you will need to edit the ports setting for that entry.
The second issue: as mentioned in the above post, is controlled by the "hide" option in the channels list window. However, mIRC will be adding an exception to this feature for double prefixes. You can test this change, and other changes, in the latest
beta.