Agree with all. Categories are must. They should be controlled via admin panel. Strong admin control in admin panel should be provided. Admin should be able to do all the required actions as mentioned in above comments.
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Sub categories are not necessary. Instedad we should also have tags for videos and so a search option. And the search should also have the option to search with tags in a particular category.
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And what about youtube videos? Please also add a feature to add youtube videos with see more youtube url.