[calorie]

It really isn't reasonable to try and list all possible combinations of available conditionals. They vary by page, mods, etcetera, so what you need to do is var_dump like already suggested, but even then those variables might not be recognized in templates. So what do you do? You are interested in 'Act as Forum' so look at the HTML source of that ACP page to see that 'cancontainthreads' is part of the input variable, and then search the code for something that might be appropriate. Here are a couple of goodies you can find:

// example_1

$forum = $vbulletin->forumcache[$forumid];

if ($forum['options'] & $vbulletin->bf_misc_forumoptions['cancontainthreads'])
{
	// can contain threads
}
else
{
	// cannot contain threads
}

// example_2

if ($foruminfo['cancontainthreads'])
{
	// can contain threads
	$show['threadslist'] = true;
}
else
{
	// cannot contain threads
	$show['threadslist'] = false;
}

Now of that, go and search the templates for all or part of a variable. For example, if you search the templates for $foruminfo then you get a list of templates where $foruminfo['cancontainthreads'] might be available. Same goes for $show['threadslist'] and other variables. Scope, order, etcetera matter so what might be available in one place may not be available in another place. Find something that looks like it might work and try it, and if there is nothing, then you can instead create it.