why is some of the function not supported when calling COM server?

[alii001]

I am using Labview to call a software, TSMaster, though COM Server.

but when dropping down the function list , some of the functions are not supported , they are gray .see as below:

So, I want to know ,in which condition will such thing happen , why ?

the second question : if COM  function originally returns an array with struction(i.e. cluster) in its developping language ,such as VC++, it will return a variant when calling then function by labview,right ? and then , I can use "variant to data" to recovery it ,right ?(the format should obey the format in VC++)