Hmm, So your Idea 1 is basically an airdrop website in a nutshell? Users get tokens for doing certain actions but instead of sharing/creating posts about the project on their FB or twitter they post it on your platform, why would anyone want to do that? Plus I don't see how your business will generate those Billions, Either you offer everyone to list their tokens for free or become something like Publish0x where you charge the developers to list their coins... I can't think of any model besides ads which will generate revenue for your business...

Decentralized search engines have already been done, you can find many projects by doing a mere google search...

Your audio app has potential as I said before, however, after doing some googling I found a couple of apps which already do this... https://musiclab.chromeexperiments.com/Kandinsky/ This one is mobile friendly and works on any device... However if you advertise and develop it properly, you can definitely make some money out of it...