Data Accessibility

I am a Master`s student at the Faculty of Science, Ain Shams University, Geology department. The University does not provide me with the required data such as InSAR imagery to Establish and interferometric time series, and the only free data I found was on ESA Hub Sentinel 1 images which have started in 2014, do u suggest any way I can acquire ERS and/or EnviSAT data.
Thanks in advance

ERS and ENVISAT data can be accessed here after free registration:

Would you mind helping me know which type of EnviSAT Data that can be combined with Sentinel 1 SLC IW data ? and, Should all the images stacked be acquired in the same flight direction, Either Ascending or Descending ?

For interferometry you can only use products from the same track.
I recommend stacking only data from one satellite and combine the results.