i bought omnibus flight controller (https://www.quadkopters.com/product/flight-controllers/omnibus-f4-betaflight-3-2-0-osd-flight-controller/).
Following is my observation.
voltage on regulator pins were like (GND, +5V and 3.3V). So, its for sure that this is 3.3V regulator. and i don't see any connection from PIN VIN to regulator.
I want to understand the regulation part. i want to know if i can directly connect battery to flight controller (i think we cannot as there is only one regulator on board). 

following are my questions
1. Can i connect battery to FC on VIN.
2. do i need another regulation for 5v.

You need externally power this fc using 5v. This fc does not do comes with 5V bec

Hello sdev,

Don't get confused between omnibus F4 V1,V2,V3 Pro. flight controllers versions.
omnibus v3 pro. only have 5v bec.

Yes, here i am not worrying about omnibus versions. I am checking with the version which i have. i have mentioned the photo. I think it has 3.3V regulator only.

Yes I have just noticed that it had voltage regulator but be careful if you are using lipo with more then 3s I have burned my Omnibus f4 pro v3 before few months ago because they are using cheap chinesee LDO and V. reg. in board.