On the sidebar go to Community → Players → click the search button → enter the userid → Follow → drag to right

• It has bullet (1-3 mins), blitz (5 mins), rapid (10 mins), classical (15 mins). You can also create a game with your own timings if you want.
• My favorite is 10+0 Rapid style.

• copy paste the contents of pgn into https://lichess.org/paste
• I did not find a way to directly upload a pgn file to their server.

• Enable the kid mode at https://lichess.org/account/kid . This will disable all site communications, communications from other internet users.

• https://github.com/ornicar/lila - source code
• https://lichess.org/features - features
• https://lichess.org/@/<USERNAME> - gives the rank ranking history of the user. For example, my history is at https://lichess.org/@/kamaraju