What is difference between SELECT * FROM table and SELECT * FROM table WHERE 1
Question 1 : What is the difference between these 2 queries, if it loads the same data.


None.


  Question 2 : Why there is these much time difference, if it loads the same data.


Within margin of error and your first query may have put them in a cache making it slightly faster.


  Question 3 : Why phpmyadmin by default loads SELECT * FROM table WHERE 1 query ?


Because it's a bit special. There are many odd behaviors of what phpMyAdmin manipulates queries in a browser to before it gets to SQL. Programmatic convenience maybe.


  Question 4 :What MySQL do for ABOVE queries in MySQL Query Caching?


Query caching is based on the literal text of the query, and some session variables. They would be cached differently.
PS. Query cache is evil.