There are some apps such as Chemistry Pro, Rankerer, M Learning, Quizrr. There are some good youtube channels as well which make easy-to-understand videos such as Khan Academy, Simplified Biology, Helios Educore, Pradeep Kshetrapal.

I would not advocate solely using apps or videos for NEET prep, these are merely supplements for your actual hardcore NEET prep (which mainly comes from NCERT and reference textbooks). Solving online practice papers is also invaluable. Making your own notes, practicing problems and understanding concepts should be your main goals during preparation.

Good Luck!

Chemistry for both JEE MAINS and NEET, revolves around the books of NCERT. I don’t believe there is any app or online tutorial as promising as NCERT. This is a very basic fact. People don’t build up questions for Chemistry. They cannot build up questions for Chemistry. They have a limited set of questions. And everything comes from that. I prefer you to read the NCERT book thoroughly. And in case you require to practice questions. That is also very important. There is an app named Quizrr.