There are no countries in the Antarctic.
There is no sovereignty on the Antarctic continent, so no official flag, currency or stamps. Whatever flag you've been told is an Antarctic flag, is a commercial venture, and represents money to somebody -- whomever is trading it or selling it. It does not represent a country, a continent or any nationality.
myanmar
Flag of the British Antarctic Territory was created in 1963.
There is no sovereignty on Antarctica. This means that there is no national Antarctic flag, currency or stamps, because there is no government to issue them. Any 'Antarctic flag' is a souvenir sold to you by a profiteer.
Antarctica does not have a flag. There are no nation-states on the continent, so, as well, there is no Antarctic currency, Antarctic stamps and so forth. Any mementos purported to be 'Antarctic' in this vein are souvenirs sold by profiteers.
Myanmar
I looked at http://www.flags-flags-flags.org.uk/honduras-flag.htm and as far as I can see, it has not changed.
Russia
There is no Antarctic flag that is a valid indicator of Antarctic sovereignty, since there is no government there. Whatever you reference is a commercial venture that requires explanation from your vendor.
yes it has been changed multiple times. the colors and shape have changed
Antarctica is a continent with no countries. There is no Antarctic flag, or currency or stamps or cities or states.
Antarctica has no official flag as it is not a nation nor is it ruled by a single government or body. so there is no national flag