Are VoIP ports blocked by ISP in India?

I need some clarification when it comes to VOIP. I read somewhere that many ISPs in India block VOIP Ports.

Is this true and if yes which services or features get affected?

Does any and every voice communication over internet falls under VOIP being blocked or when we say VOIP is blocked it mainly refers to PC to Phone Line (Landline/mobile) communication?

Do video calls (PC to PC / from one user to another) done using Skype/Google hangout etc get blocked when ISP blocks VOIP port?
Thanks.