Also, the amount of spaces required will differ from the original text. If you want a safe allocation, we might need to alloc (2 * strlen(text) + (strlen(text)- 1))). Because for each possible letter you are allocating 1 extra byte for safety, and 1 extra byte for space, excluding the last char(hence strlen(text - 1)). In case the string is, for example "Abcdefghijklmonpqrzx" - no spaces at all, and letters that do consume 2 bytes - this will work, whereas allocating for strlen(text) wont.

strrev does not exist, thus code does not work if n exceeds 26 with lower case values, will overflow the char
you make 2 allocations, thats not really usefull

you should use 'a' and 'z' instead of 97 and 122, because those values does not mean anything when we read them

if arr_size equals 0, your size_t underflows and you might crash

tho the for without a first argument is disgusting

easy to make it crash