All of the example sentences you give could mean you did the work yourself, and two of them can only mean you did the work yourself, BUT the structure you give in the title is not the structure of those sentences.
The structure in the title, [ Subject + "get" + object + past participle ], is called causative, and it always means someone else did the work at your request.
The structure of the example sentences you give is actually, [ Subject + "get" + object + adjective ]. We can show this is true because you correctly use the words "open" and "complete", which are never past participles in that context, only adjectives.
The function of this structure is something like, "cause object to become adjective", or "get object to be adjective".
The two structures sometimes look identical because some adjectives are spelled and pronounced the same as a past participle, like "finished" or "painted". So, your example sentence, "I got the fence painted" is ambiguous. It could have the meaning, "I paid someone else to paint the fence", or "I completed the job of painting the fence", depending on whether "painted" is intended as an action verb that someone else performed, or an adjective describing the state of the fence. Out of context, a native speaker would not know which had happened.