Well it takes me a while to read through all these questions and figure out the answers. Sorry. XD
A1: You can prevent it from removing 'rn' by opening script file abstract_messagecontainer.php and remove this line in method format():
PHP Code:
$text = str_replace("rn","",$text);
You can remove the other lines in the method format() too. However, I must warn you that there is a reason why 'rn' is removed from user submitted data, you will notice them once you make these changes.
A2: I believe in Mys v1.3.3 the shoutbox page automatically refreshes after like 5 secs? Does this functionality not working properly for you?
A3.1: Yes it is possible, but will likely require you to modify the forum script. This is kinda tricky since MyBB is also constantly upgrading, who knows what their script looks like in the next version? Note the current forum integration script is set up in a way that you can upgrade your forum script freely, if you edit your forum script files you will lose this benefit. The more feasible way is to create a plugin for MyBB as a third party script without modifying the core script of MyBB, it is not that easy.
A3.2: This is doable, assuming your adoptables site and forum site have the same user id(otherwise it may be a bit confusing in terms of userid mapping). You should be able to get a formula for your forum profile url such as forum/user/1 or something like that. All you have to do is to create a module at your sidebar with a link written as php code referencing to your forum profile. If you want it to appear in your dropdown menu or sidebar links, it can get a bit tricky since you will need to get the corresponding GUI link object and edit it. I will show you an example of how to achieve this if you want to.
A3.3: This should be easy, all you have to do is to find the script where site avatar is being inserted/updated in database, and then insert/update the same record in your forum database. Note for users with default avatar, the relative url can be a bit of problem.
A4: Looks like you are requesting a mod/plugin to be made, I am not sure if I take requests like this right now since I have both school and Mys v1.3.4's development to worry about. Perhaps another user will help you out, or you may seek for some inspirations from how I did the itemdrop Mod?
A5: Definitely yes, and should be easy. The item function can be completed in a few minutes, but you will need to insert a row of data into the table prefix_item_functions so that this item function will be recognized by the system. Otherwise you wont be able to manipulate it through ACP.