UCL MSci but want to do MSc to another university

will I be given the graduation certificate for the BSc if I'm on the third year MSci but will cash out and go to the MSc in another university?

Thanks for answering! We can choose the project for MSci. I just want to make sure that I can go to the other MSc if I’m on the MSci cuz the final result will come out around the start of July and according to the result I’ll decide whether to take MSc or still continue MSci.

Your post is kind of hard to understand exactly what it is you are asking and what you are aiming for.

You can do an undergraduate MSci, graduate with the undergraduate MSci, then do a standalone 1 year postgraduate MSc elsewhere. Absolutely nothing stopping you from doing that (except, possibly, the financial side of things).

If you wish to not continue to the fourth year of the MSci for whatever personal reasons, as above you may be able to supplicate for the BSc if you are in final year now, or may be able to switch to the BSc if you are in first/second year, but you will need to liaise with your department to understand the process and if this is possible.

However if the question is in the context of you potentially failing to achieve the result required to progress to the fourth year of the MSci then you will usually be given an exit award - but what that award is will likely depend on the result. However if you do not achieve the standard to progress to the MSci fourth year you may not have a strong application for a standalone MSc with whatever exit award you get (and some exit awards e.g. an ordinary degree may not be suitable for posgraduate study).