Change in ITR from employee to entrepreneur

Hi, 

I was employed till 2020 and was filing ITR 1. Now I am a full-time entrepreneur and have income from my venture and interest income. I have not maintained books of Account so far.

1. Which ITR should I file from the current year onwards? ITR 3 or 4?

2. Should I maintain books of account from the Current year onwards? If Yes, then can I include all the previous assets (stridhan etc)? Will that  have any impact?

Request for a prompt response, since we are left with just 3 days for ITR Filing. 

Thanks.