Can I do bsc from a regular college while learning coding online , can I still get as software engineer, is that possible?

Ans: There are multiple advantages of joining an offline education program.
1. You get plugged to a community that also has the same goals as you do
2. You foster relationships that will stay with you for life and also help you succeed in the longer run
3. Accessibility to teachers is not limited to a pre decided slot, and they are easily reachable on the campus
These and more reasons have also motivated us to create our 4 year residential Bachelors program. You can explore more at https://www.scaler.com/school-of-technology/

Ans: You can do, but for that again you have to do a diploma in Computer Science. You can't go directly from Civil to Computer in India. Otherwise you have to clear 11th and 12th Science (I am assuming you joined diploma after Xth Standard) and take fresh admission in Computer Science. But it will be a great loss of time. The best way is to do online BBA. It will give you graduation ( though for BBA 12th pass is essential) and after BBA you can do some good certificate course from institute like INTELLIPAAT which gives standard certificate in Data Science and Machine Learning (a need of the day) in Collaboration with IIT- Chennai/IIT- Roorkee. It will create a path for you to go in the stream of computer science. Join me in LINKEDIN for permanent connectivity and counselling. GOD BLESS YOU. Professor...........................:)

Ans: Full-time Offline BTech (Best Option for Engineering Career)
If your goal is "to become an Engineer", a proper BTech (even lateral entry) is the best option.
Since you already have a BSc in Mathematics, you might be eligible for lateral entry into 2nd year of BTech via LEET (Lateral Entry Entrance Test) in some universities.
If possible, doing an offline BTech in fields like CSE, ECE, or Mechanical would give you the same standing as a BTech graduate.

MSc CS or MCA + Engineering Diploma
MCA is a well-respected degree in the software industry and is often considered equivalent to BTech in CSE for many IT jobs.
An MSc in CS is more academic/theoretical and is better suited for research or data science roles.
A Diploma in Engineering (Distance/Online) will give you technical exposure, but companies may still prefer a full-fledged BTech over a diploma.

Ans: It is not realistic at all. A BSC can't do the job of an engineer. I think you have asked this question for 2nd time.