beginner questions about chess

What is the best chess website for free chess puzzles?
What are the differences between the most popular online chess websites where one can play games?
What tactics/strategies are best to use in 1 minute chess games? (for a beginner with 700 ELO rating) https://nox.tips/ 
What is the most effective way to increase my 700 ELO? (practising hard is not as effective as practicing smart. Any tips?)

I got this,...

Its at least poor taste, if not a violation of forums, to link competition sites here. 
1 min games are too fast for beginners, but at 700 rating, your strategy would be to simply not drop pieces to simple blunders.  doing that should put you over 1000, and ready to visit additional ideas.  It helps to know your opening and ending cold so you can do them fast.  

to improve your rating, try playing slow games where you can think and see more.  Speed comes with familiarity, so playing quality games at a slower pace WILL help your fast play too. 

I think it's OK to mention other puzzle websites, lots of other players here use them. A lot of people rate Chess Tempo quite highly.

I don't know how to improve at 1 minute chess because I don't play it. I am around 1300 rapid and I literally cannot play 1 minute chess, so I can only wonder how useful it is for you to play.

In terms of improvement, where exactly are you looking improve... just your bullet and speed chess or with general chess principles?

A great puzzle website is www.ChessByLauren.com!  

There's over 450 puzzles here for the beginner and the puzzles are endorsed by chess masters and other respected top players!  

Questions 3 and 4 are actually connected. The answer to both is: "Don't play 1 minute chess". That is just complete nonsense at the 800 rating level.

Sure, but Lichess is much better. Unlimited puzzles and also when you fail or get a puzzle right it finds the right puzzles for you. There is also puzzle storm or puzzle racer, but it's your own opinion.

@1
"What tactics/strategies are best to use in 1 minute chess games?"
++ Do not play 1 minute. Play 15|10 rapid.
"What is the most effective way to increase my 700 ELO?"
++ Always check your intended move is no blunder before you play it.
Whenever you lose a game, analyse it thoroughly to learn from your mistakes.

Improving Your Chess - Resources for Beginners and Beyond...

https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond

Hi! My name is Lauren Goodkind and I’m a respected  chess coach and chess YouTuber who helps beginners out : 

https://www.youtube.com/channel/UCP5SPSG_sWSYPjqJYMNwL_Q

Send me one of your games and I'll be happy to analyze the game for free on my YouTube channel on Sunday livestream from 1-2PM PST.  Ask me questions in real time!  

 This is a great way to improve!

Regarding the best puzzle webiste, I suggest this one: 

.  These puzzles are endorsed by chess masters!