How to get timeDim ie months in reverse starting with curr month followed by prev months? in columns

if I understand correctly, you need that in the cube view, right?

In this case I'll build a quick XFBR function with the following key functionality. Please note, I oversimplify few thing there for easier read/understanding. 

' Say, your current period is your pov, that you are passing with Time parameter in which case
'XFBR(XFBR_Name, ThisFunctionName,Time=|POVTime|)   <This is how you call it from the cube view
Dim strTime As String = args.NameValuePairs.XFGetValue("Time")
Dim intCurrentPeriod As Integer= BRApi.Finance.time.GetPeriodNumFromId(si, strTime)

Dim strReturn As String = string.empty

For i = 0 to intCurrentPeriod

strReturn = strReturn & "T#" &  BRApi.Finance.time.GetNameFromId(si, BRApi.Finance.time.AddTimePeriods(si, i * -1,True)) & ","

Next

' Get rid of the trailing comma

strReturn = Left(strReturn, len(strReturn-1))

Return strReturn

There are many ways to skin this cat, thought, including loop with step -1 etc.