Hey guy, you should give us the context or example because these rules depends on the specific context. I can give you example with two rule above.
We have to consider selling
the house. => -ing is role of NOUN
I'm used to playing
football => -ing form plays a role of Nound before preposition "to"
I look forward to reading
book. => -ing form plays a role of Nound before preposition "to"
If you can give your example and your choice, we will correct more specifically.
Hope that helps
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