colleges accepting UPCAT

As you already known that the best college of UPTU is HBTU, but is no more part of this organization. So, for CSE, you can try IET-Lucknow, but I will say your college does not depend but your branch depend upon placement, and CSE is extremely good branch in whatever college you got.

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

There are 20%-30% seats are reserved for the students who are taking lateral entry in every college. The seats reserved for lateral entry may differ in some colleges. The fees for the degree engineering course may differ from college to college. So, you have to go through college and know yourself better. All the best. Lateral entry students seats are depending on the college that you have preferred for yourself as each college have its own quota for Polytechnic students. Fee structure is also depend upon the college that you prefer the most.

No, but you can get top private colleges like JSS Noida, AGK and KIET.

Try for RKGIT or GL Bajaj.

UPSEE 2018 College Predictor
Use your UPSEE 2018 rank to see where you can GET admission at the link provided below:
See the courses, colleges & rounds you may crack
The result is based on admissions data of UPSEE 2017
Get resources & insights on colleges & courses
https://www.shiksha.com/b-tech/resources/upsee-college-predictor.

There are over 12 B.Arch Colleges in India offering 12 courses, which accept UPTU scores and ranks. Please refer to the link provided below for a detailed list of these colleges. You should be able to navigate to a college of your choice using the filters on the web page. Regards. https://www.shiksha.com/architecture-planning/colleges/b-arch-colleges-india?uaf[]=exam&ts=55372543&rf=filters&bc[]=5&ex[]=6612.

Yes, you can get a government college through UPSEE with a score of 260 in UPSEE. Unfortunately, you can't compete yourself in that race. I would recommend you to either drop this year, and try with better knowledge next time, if you really want to be in a government college, else Ill recommend you to just take admission in a private university, not private college of AKTU.