I would like to ask that my visa start 16.08.20 and my flight time is 16.08.20 at 00:15 !! Is there still problem there to check in and go through Immigration before my visa start?
If your flight departs fifteen minutes after your visa's validity period begins, your only problem is that your visa won't be valid when you check in. This shouldn't be a big problem. It's certainly acceptable to the visa authorities, but you might encounter an airline employee who is overly cautious. If so, point out that your visa is valid on arrival.
If your flight arrives fifteen minutes after your visa's validity period begins, you have the same problem, but it's more likely that airline employees might be overly cautious.
The other problem with the second case, of course, is that flights routinely arrive more than 15 minutes early. In that case, you can just wait until midnight.
But if you can reschedule your trip a day later, you will probably have a less stressful time of it.