To accede to something is to agree to it: I accede to your request (I accept it); to concede something is to accept it grudgingly or reluctantly: I concede your superiority (I have to admit you are better). Spelling: remember the ending -cede.
The flags of Qatar and Bahrain are very similar, reflecting the countries' historical links. The proportions of the Qatari flag are unique. Effective date: c. 1949.