This conversation seems to be going no where. Forum members have given you advice given you were tried and convicted of a crime which carries consequences. As you know this is only a public forum and not staffed by anyone in the legal profession.
If you are still not convinced then you either need to consult an immigration lawyer or take your chances and simply apply to immigration ensuring you declare your conviction. Not declaring any conviction will simply add to your problems, as you say we do not really know the whole story but in the end you were convicted of a crime regardless so just accept the consequences.
Immigration do not care whether you are enrolled in a course or not, you are in the country as a temporary resident with limited rights to stay and must as everyone else obey the laws. If you do not there are consequences that you must accept.