I want some old tweets on mobile device to proceed in my research. Tweets should contain any mobile device name or handle. Where can I get old tweets?
In April 2010, the American Library of Congress announced that it would archive all Twitter tweets. In 2013, they announced that they had archived all tweets between 2006 and 2010.
However, an article in The Washington Post from January 2013 also said that these tweets had not yet been indexed in a meaningful way. And in July 2015, Politico wrote, Library of Congress' Twitter archive is a huge #FAIL: even purely academic research on the archive appeared impossible.
I am not aware of other libraries who ventured to archive Twitter tweets.
(If what you want is just access to your own old tweets, you should have checked services to back up your tweets. See, for example, 4 Cool Services To Backup Your Twitter Stream, 12 Tools to Backup and Archive your Tweets, Frostbox, etc., etc.)