Self Assessment for both self-employed (sole-trader) and non self-employed (CGT, interest ...)

I am first time tax payer, for self assessment ("SA") for both self-employed (sole-trader) and non self-employed (CGT on stock investment, interest ... etc), is that I have to register for SA separately and get 2 different UTR nos.?

No you just need one UTR number.

but when I register for Self Assessment at "https://www.gov.uk/register-for-self-assessment/y", the first question is asking if 1. You're self-employed (for example, a sole trader) or 2. You're a partner in a business partnership or 3. For another reason (for example, you have income from a pension or a property) I can only choose one, but for my case I am both "1" and "3".

Hi
No - you only need one UTR. At the end of the tax year, you declare all of your income, including investement and Self-Employment income, on the same tax return, using this UTR. 

Hi Peter,
Choose 1, as you will also need to register for Class 2 National Insurance.
Thank you.