Regarding the three posts above:
- OP cannot just "elect" to be a resident of Canada within the meaning of the Income Tax Act, RSC 1985, c 1 (5th Supp). If OP is not a resident of Canada, then he or she is not a resident of Canada. It doesn't matter whether she or he is getting a benefit from this; it can't be changed without the facts changing.
- Lying to immigration officers is a very bad idea. I discuss this more below.
In the OP, the first question asks what the OP can do to enter countries other than Canada without trouble. The first thing to understand is that, as a matter of international law, OP does not have any right to enter countries other than Canada. "It is a received maxim of International Law that, the Government of a State may prohibit the entrance of strangers into the country." Arizona v. United States
, 132 SCt 2492, 2511 (2012) (opinion of Scalia J, dissenting but not on this point) (internal quotation marks and citation omitted). The OP appears to be approaching this problem as if he or she has the right to enter countries and the question is just how to exercise this right. As a matter of law, that is the wrong perspective.
Turning to the correct approach, countries have the power to decide which foreigners they will admit into their country and, in countries that follow the rule of law, the criteria will be prescribed in statute or other written instrument. Before planning a trip to a given country, the first thing to do is ascertain is whether you actually have the right to enter that country. Many countries do not permit you to visit unless you have a residence in another country. For those countries, if you have no residence in another country, you are not allowed to enter
. Thus, before planning to visit a country, OP first needs to determine whether having a residence nowhere is a problem. If OP is not permitted to enter a given country, then she should not attempt to enter it, rather than engaging in fraud as two of the posters above suggest.
As for the UK in particular, the power to control who can enter the country is within the power of the Queen, which power is exercised on her behalf by the Home Secretary. The Home Secretary has in turn promulgated a set of written rules describing how his or her discretion will be exercised. "The status of the immigration rules is rather unusual. They are not subordinate legislation but detailed statements by a minister of the Crown as to how the Crown proposes to exercise its executive power to control immigration." R (on the application of Alvi) (Respondent) v Secretary of State for the Home Department (Appellant)
,  UKSC 33, ¶ 9 (internal quotation marks and citation omitted). A review of the relevant rules for visitors reveals that there is no specific requirement to have a residence outside of the UK. However, the proposed visitor must satisfy the immigration officer that, among other things, the proposed visitor "will leave the UK at the end of their visit" and "will not live in the UK for extended periods through frequent or successive visits, or make the UK their main home". Immigration Rules
§ V 4.2.
OP should review all of the immigration rules but it looks like OP may qualify to enter as a visitor despite not having a residence outside of the UK. This possible conclusion is further backed up by the fact that the immigration officer in OP's story actually allowed OP to enter the UK. Why did OP have difficulties then? It was most likely because OP had a poor attitude
when making submissions to the immigration officer. The OP appears to approached this situation as if OP has the right to enter any country she or he wants (which is wrong), and that kind of attitude comes out in how people to speak to immigration officers, and always leads to a bad time. The correct approach is to be respectful and demure. Anything you say should be tailored to explaining how you meet the requirements in the rules. If the officer tells you not to use your phone, then you do not use your phone. If OP needed to contact her or his son, he or she should have asked the officer for permission. Generally, OP's problem was almost certainly rooted in her general approach to making submissions, rather than a failure to meet the requirements.
For countries other than the UK, the situation may be bleaker as OP may not actually be permitted to enter without a residence elsewhere. I would strongly advise not lying when attempting to enter these countries, contrary to the advice other posters gave above endorsing fraud.
As for the second question, the OP asks about possible immigration problems when entering Canada. Again, OP should just tell the truth. There is no need to be concerned when entering Canada because, under the Constitution of Canada, "[e]very citizen of Canada has the right to enter [and] remain in ... Canada". Canadian Charter of Rights and Freedoms
(Part I of Constitution Act, 1982), § 6(1). If you are a citizen of Canada, you cannot be excluded from Canada. In fact, even if you don't have a Canadian passport, you still have the right to enter Canada if you are a citizen (although it might be a bit harder to prove that you are a citizen).