Architecture

Both the institutes are average in terms of faculty and placements, I would advise you to join some other better college.

No, you cannot do architecture if you are from commerce stream. From 2018 onward, only science (PCM or PCMB) students who have scored atleast 50% in class 12th with mathematics as compulsory subject will be considered eligible to appear in architecture entrance exams.
Before 2018, commerce with maths students who did secure atleast 50% in class 12th were eligible to appear in architecture entrance exams.
Check this link-
http://indianexpress.com/article/cities/mumbai/arts-and-commerce-students-wont-be-able-to-pursue-barch-from-2018/

For these minute details, I advice you to contact the college authorities for precise information.

Yes, if you have diploma in civil engineering you can surely get lateral entry in B.Tech architecture but some colleges has some colleges on their own rules. Most universities usually take the lateral entry for civil engineers to the B.Tech architecture you can surely search for that.

Considering you fall in general category, you will get the lower branches in NIT, Allahabad and top branches in NE, NITs and other lower NITs. If you are interested in core branches then better take RV, Manipal or VIT.

Hi Gayathri,
The cutoff varies every year according to the number of students applying for examination and number of seats available. It would be advisable that you get in touch with college authorities/official page directly for accurate cutoff.

Niranjan, it is not possible as they are two different courses. You need to take admission from first year onwards in the new course.
For more information, you can check with some reputed universities like Lovely Professional University, Chitkara University, Chandigarh University, Rayat Bahra University, etc. All these universities have wonderful infrastructure and world-class facilities to offer to students apart from good placements that they offer.
Good luck.