Does Telegram use end to end encryption by default yet, or does it still send and store everything except for secret chats to the Telegram service in plaintext?

Does Telegram use end to end encryption by default yet, or does it still send and store everything except for secret chats to the Telegram service in plaintext? Also, when you use the secret chat feature does that now support multiple clients or does it still establish a secret chat with a random recipient client over which neither initiator nor receiver can control?