CRM 2016 Data Import - Limitations ?

Hi All,
We have a requirement to Import bulk data(more than 1 million) in CRM 2016, Need clarifications on the 

below mentioned questions

1) WHAT ARE THE LIMITATIONS(SIZE(other than 32MB file) /NUMBER OF RECORDS) for DATA IMPORT IN CRM 2016?

2) We have created a custom Application to import data in CRM from Excel sheet. How long it will take to 

import 1 Million records in CRM 2016. (Note:1 Million Records with 50 fields(Columns)) ?

3) Is it possible to import 1 Million records (Excel to CRM) in CRM 2016 using CRM OOB data import 

wizaard funtionality ?

4)  Is there any limitation for Data import using custom application (Dot net application)?