Certificate

Hello,
Actually, it is you who is going to decide whether it is worthy or not. If you have done a course related to it through regular mode then you may take a chance to go for the correspondence mode.
However, my suggestions are:
1. If you have any full proof plan then you may go for that. If you think that you can do well in voice culture without going to any coaching center or institute then yes, you may do so.
2. Only think about distance learning in professional voice culture, if you are doing any relevant job simultaneously. It will give you practical job experience in parallel to your studies.
Hence, now you are may be getting the point to whether go for distance learning or not.
I hope you are getting the point.

An advanced certificate (Considering it as something done from a reputed place as well as after graduation).
The answer that I gave for PG in Advertising Management prospects abroad and in India seems appropriate here:
An M.Sc in advertising management is a very popular-innovative as well as the less taken domain of studying mass media or mass communication. While doing the course, one learns how to see the need, plan, use the USP and create USP of the product in hand. The management of advertising of a particular product is to be done to see the impact. Along with this, the question demands response to career prospects for public relations. Public relations, on the other hand, has similar notions. The jobs that can be done abroad or in India after pursuing an M.Sc advertising management as well as a Public Relations Management degree are:
1. Teaching
2. Research
3. Job in a News Channels
4. Consultancy to get the Advertising Campaign done of a brand
5. Public Relationship Agencies
6. Event Management
7. Counsellor and Trainer
The above profiles can be developed for a job in the Advt. Management space.

Hello,
To be more specific for your query, it is not worthy. If you are willing to make a career in acting and modeling through distance mode, I would like to say certain points:
(#) If you are very much aware of the current Bollywood conditions and trends, you don't need to be much qualified. On screen, what matters is your acting skills and how you present yourself. These qualities and skills cannot be generated from obtaining the certificates. These are generated through regular practice and on-stage demonstration. So, you don't have to go for any advance certificate in film and modeling course.
(#) If you think that getting the certificates is extremely important for you. Then you may. But don't go for distance learning mode. These are the certificates which give you quality, skills. And you can never master any skills while sitting at home. So do only through regular mode.
Hope this helps.
Upvote the answer if you feel satisfied.
Good luck.

Audio-video editing is technical learning and will need some language and other mass media skills to bring growth in career.
The certificate you are pursuing in editing and proof reading is a good way to join the media jobs, as content writing and content editing-proof reading is quite a good career. From media/journalism writings to website developments, this task has a role.
You may think of the following courses depending on the qualifications you already have:
1. If the current course is done after doing graduation then a Post-Graduation in mass communication/mass media/media production can also be good for you. I shall not hesitate to suggest even a Master Degree in a language- English, Hindi or the one you see as an additional strength for editing and proofreading works.
2. If one does certificate in proofreading and editing after class 12th, pursue graduation as a must to do thing. Any stream you may choose keeping in mind that an alternative career has to be met openly. Proofreading and editing job can also be a part-time thing so you have enough time to do another degree or higher studies.
3. If this certificate course is done by someone who is a Master Degree Holder, if not in language or social science, humanities, do one degree.

Non-linear editing is a specialisation domain, and there may be many things that you will need to keep learning along with the production learning.
The suggestions that I can make are:
1. A degree in a popular language that shall be used in your works and place.
2. Content writing and proof reading.
3. Web development and digital marketing.
4. Music and sound mixing basics/audio production.
5. Advertising and public relations management.
The decision depends on how much time you get free from the work of learning documentary production. When you say that you are learning the production of documentary-I take it as a comprehensive work that is itself a time-taking thing and might not allow you to venture for more.

Documentary production/cinematography is a specialisation domain, and there may be many things that you will need to keep learning along with the production learning.
The suggestions that I can make are:
1 A degree in a popular language that could be used in your work place
2 Content writing and proof reading
3. Web development and digital marketing
4. Music and sound mixing basics/audio production
5. Advertising and public relations management
The decision depends on how much time you get free from the work of learning documentary production. When you say that you are learning the production of documentary, I take it as a comprehensive work that is itself a time-taking thing and might not allow you to venture for more.
Read the related question which gives a similar solution:
https://ask.shiksha.com/what-parallel-courses-can-i-pursue-with-a-certificate-course-in-radio-jockeying-for-better-career-prospects-qna-4393561