To turn Hana into anaH, Excel 365 can do it with one formula. In older versions, use a one-line VBA function, or Power Query’s Text.Reverse.
Excel 365CONCAT + MID + SEQUENCE
Any versionStrReverse in VBA
Power QueryText.Reverse
Table of Contents
1. Formula (Excel 365)
=CONCAT(MID(B3,SEQUENCE(LEN(B3),,LEN(B3),-1),1))
| Step | For “Hana” |
|---|---|
LEN(B3) |
4 |
SEQUENCE(4,,4,-1) |
{4;3;2;1}, counting down |
MID(B3,{4;3;2;1},1) |
{“a”;”n”;”a”;”H”} |
CONCAT(...) |
anaH |
TEXTJOIN works too: =TEXTJOIN("",TRUE,MID(...)).
2. VBA function
Add this to a module (Alt + F11 → Insert → Module), then use =ReverseText(B3) like any function:
Function ReverseText(s As String) As String
ReverseText = StrReverse(s)
End Function

Save the workbook as .xlsm to keep it.
3. Macro for selected cells
Writes the reversed text in the column to the right of each selected cell:
Sub ReverseSelection()
Dim c As Range
For Each c In Selection
c.Offset(0, 1).Value = StrReverse(c.Value)
Next c
End Sub

See also the reverse text macro.
4. Power Query
Add Column → Custom Column with Text.Reverse([Names]).

More: reverse text with Power Query.
Reverse the word order instead
To turn Christopher Edward Nolan into Nolan Edward Christopher in Excel 365:
=TEXTJOIN(" ",,SORTBY(TEXTSPLIT(B3," "),SEQUENCE(,COLUMNS(TEXTSPLIT(B3," "))),-1))