data structure i really need for clear and briefly explanation thank you so much

Is 2n+1=O(2n)? Question 2) [2 points] Is 22n=O(2n)? Question 3) [2 points] Explain why the statement, "The running time of algorithm A is at least O(n2) " is meaningless. Question 4) [2 points] Using reasoning similar to what we used for insertion sort in class, analyze the running time of the selection sort algorithm from the first homework assignment. Question 5) [2 points] Why do all cases have the same runtime in selection sort