1) I run a Youtube channel on cooking recipes . Can I use the same videos on Udemy ? Are there any copyright issues etc. as the videos are my own intellectual property.
As far as I know as per Udemy policy, you can not offer something PAID on Udemy which is FREE outside, if it is FREE on other platform, it must be FREE on Udemy, if it is PAID on others it can be either PAID/FREE
2) How does the revenue model work in case I choose to go for free course .
If you make a free course, you will not get any payment for enrolments and registrations obviously, you will only get paid when you make a paid course and someone buys it
3) If I have content less than 2 hours then will it have mandatory classified as free course ?
No, a PAID course can be of any length above 30 minutes, 30 minutes if the minimum requirement to get published, a FREE course must have below 2 hours, means if your course is beyond 2 hours, it can not be distributed as FREE on Udemy platform.
4) Can I have my course in other regional non english languages like Hindi?
Yes, you can have, Udemy put no restrictions on language, however, Udemy most market is English speaking. I have a course in Hindi/Urdu but no one ever buys that I have same course in English which sells like crazy