Function (B) has time complexity of O(n)

Function (D) has O(1)

Now, I Re-write the return statement of A as

return $A(\sqrt n)+O(n)+A(\sqrt n)+O(1)$

So, I form my recurrence for A as

$T(n)=2T(\sqrt n)+O(n)$

How Do I solve it?

Function (D) has O(1)

Now, I Re-write the return statement of A as

return $A(\sqrt n)+O(n)+A(\sqrt n)+O(1)$

So, I form my recurrence for A as

$T(n)=2T(\sqrt n)+O(n)$

How Do I solve it?