UPCAT

You need following originals at the time of counselling:
Your counseling letter
UPTU score card
Your original marksheetsMedical certificates
Caste certificate
Domicile certificate
Income certificate

If you have the potential to crack NEET then you can drop. Don't lose hope until you can’t achieve your goal as I know that MBBS is your goal but if don't have potential then you can take admission in biotechnology.

You can take admission in any private college for CSE. You can consider following colleges:
ABES Institute of Technology
Meerut Institute of Engineering and Technology
Babu Banarasi Das Northern India Institute of Technology
Babu Banarsi Das Institute of Technology

Yes, you can get admission for B.Arch and in colleges such as:
IET, Lucknow
Faculty of Architecture
Netaji Subhash Chandra Bose

You can get government colleges such as CSJMU, MJPRU, CIPET, etc.

Lateral entry depends on vacant seats in 2nd year. I don’t think you will get government colleges but you have 60% chances for Galgotias.

Yes, you will get Galgotia University on the basis of your OBC rank. Make sure you have proper OBC certificate otherwise you will judged as a general candidate.

Use Shiksha's college predictor to know about college:
https://www.shiksha.com/b-tech/resources/upsee-college-predictor