Is uploading music to spotify still possible?

If it's your own music going out through a distributor, claim your Spotify for Artists profile once the first track is live. That's where you get the stats, can change the bio and photo, and pitch unreleased songs for playlists. Podcasts are the one thing you can still upload to Spotify yourself, through Spotify for Creators. Music has to go through the distributor though.

Depends what you mean by uploading. If you want your own songs out on Spotify for other people to hear, you can't put them up directly, you go through a distributor like DistroKid or CD Baby and they deliver it. If you just want your own mp3s inside your app, that's Local Files. On the desktop app go into Settings, switch on Show Local Files and add the folder they're in. Put them in a playlist and they'll download to your phone if it's on the same wifi as the computer. Mobile playback of local files needs Premium as far as I know.