Is it possible to change university during corrections on CSP or during visa appointment?

I got into university A but interested in university B and still waiting for results from B. I applied for visa with uni A's admit and got some corrections on CSP portal. I didn't submit corrections yet. I didn't enroll in university A.

I have below concerns:

1. is it acceptable to change university during corrections stage on CSP? Technically I am able to edit fields.
2. is there any deadline to submit corrections on CSP?
3. is it possible to change university during visa appointment?