Return Different Column Value in Same Row Context after CALCULATE

Hi all,

I hope everyone is doing well. I am new to PowerBI and am currently working with Salesforce data to analyze historical opportunity changes. The data I am currently working on looks something like this:

This data is a hisotry of changes made to the opportunity. At first, I only had the first three colums (Opportunity ID, StageName, CreatedDate). Looking for a way to measure the time between different entries, I stumbled upon this post from 2017 of someone who was trying to do the same thing as me. Following the solution to this post worked perfectly, and is what gave me both the Index and NextStageCreatedDate. Here is the solution that was provided:

1. Open query editor. Sorted by "OpportunityId";
2. Open ADVANCED EDITOR (Sign 2), then add ", {"CreatedDate", Order.Ascending}" (sign 3).
3. Click DONE, you will see two sorted arrows (in yellow square).This is what we want.
4. Add index.
5. Add a calculated column with this formula.

NextStageCreatedDate =
VAR CurrentIndex = 'Opportunity History'[Indexnew]
RETURN
    CALCULATE (
        MIN ( 'Opportunity History'[CreatedDate] ),
        ALLEXCEPT ( 'Opportunity History', 'Opportunity History'[OpportunityId] ),
        'Opportunity History'[Indexnew]
            = currentindex + 1
    )

This code will return the next CreatedDate for an entry with the same OpportnityID; if there are no next entries for that OpportunityID, the field will be left blank. 

Now that I have the NextStageCreatedDate column created and working, I am now trying to create a column that will give me the StageName the OpportunityID was previously at before being changed. Seeing as the row context will have the same exact criteria as above, I thought it would be best to keep the same funciton and alter it slightly to instead return the StageName. I first altered the code to pull from the previous entry as opposed to the next. To accomplish this, I changed

= currentindex + 1

to 

=currentindex - 1

Current issue: I am not sure how to alter the formula to return the StageName rather than the CreatedDate. I have explored using RELATED, RELATEDTABLE, and LOOKUPVALUE, among others (but I'm not sure where I should input these, if they are correct). Since the CALCULATE along with MIN and ALLEXCEPT is used to determine the correct row context as well as ignores filters, I believe I need to (or should) keep it when determining the previous stage. When determining the previous StageName, I want it to calculate the row context in the exact same way it did for the NextStageCreatedDate (outside of me changing the last line to allow for previous instead of next), but instead of returning the CreatedDate it found, I would like the StageName from the same row (in the same table) as the CreatedDate was. Additionally, rather than returning a blank if there is no previous entry, I would like it return "First".

Could anyone help me figure out how I could accomplish the above? Since I'm new to PowerBI, I would greatly appreciate any explanations or advice you may have that could help me along my journey. Thanks in advance all of those that take time to help me out with this.