Yes, you can purchase Vivo V11 Pro via without credit card option. Check out this video - this will help you to understand the whole process.
Yes, Vivo V11 Pro does have the OTG support.
No. Vivo V11 Pro does not have the notification LED light but it does have the always-on display.
Vivo V11 Pro is very much eligible for the software update. The phone comes with Android 8.1 out-of-the-box. However, Vivo has not yet announced the further upgrade of the software.
The Vivo V11 Pro is a solid all-rounder at Rs. 25,990 and offers better value than the Oppo F9 Pro (Review), but for a bit more money. Think of it as a Vivo X21 with a bigger battery and better front camera, but at a much more reasonable price, which is a good recipe.