To download Facebook leads with all the columns as per your lead form, you need to understand that Lead Centre provides an aggregate result on each download whereas your lead forms might differ from each other in terms of the Q&A columns they carry.
Confusion is in the leads directly downloaded from the Leads Centre, as the leads downloaded from this section are in a composite type and do not contain all the columns as per different Lead Forms.
This further creates problems if you don't know how to find the leads against each lead form. To find and download every column your lead form contains, it is always better to download the leads for each form separately.
Go to FB Business Suite https://business.facebook.com/latest,
Click on 'All Tools' from the left side navigation panel,
Go to 'Instant Forms', which can be directly accessed from https://business.facebook.com/latest/instant_forms/forms,
Select the form you want to download the leads from,
Click the 'download' button present besides 'create ad'
Now select the date range for the leads and click on either CSV or XLS,
Your leads will start getting downloaded now.
VISIT BUSINESS SUIT:
CLICK ON ALL TOOLS:
FIND & CLICK ON INSTANT FORMS:
SELECT THE FORM:
SELECT THE DATE RANGE:
SELECT EITHER CSV OR XLS:
FIND IT IN THE DOWNLOAD FOLDER
The final excel/CSV file will contain all the columns from the lead form so selected.