hi, thanks for your kind help. looking at http://analysis.cpuchess.com/ , how do you actually start a game on it? I press play w , move a piece and nothing happens
online chess engines

No, no, no ....
That's all you need. It's regularly updated. The only other engine to think about using other than the most updated version of Stockfish Dev is Komodo 9.x but you wanted free so ...that leaves Stockfish Dev.
Stockfish Dev is slightly more tactical while Komodo is slightly more positional. They're both amazing though.

hi, thanks for your kind help. looking at http://analysis.cpuchess.com/ , how do you actually start a game on it? I press play w , move a piece and nothing happens
Just go to Lichess if you want to play against the newest version of Stockfish. It's free and you can import games for local analysis, too.

Is it allowed to use engines in Online Chess?
Not on this site: it will get you banned if you are caught

The only one cheating are the ones not cheating. Anyway since the aforementioned ending can be found in Fine it is good to know the rules are still the same, the pawn chain and the fifth rank.

"Certain forms of assistance, including books, chess databases and sometimes chess programs, are often allowed. Books and databases are almost universally acceptable, but organizations vary as to whether chess engine use is permitted." - https://en.wikipedia.org/wiki/Correspondence_chess#Server-based_correspondence_chess
I was wondering if it is allowed here
are there any free online chess engines i can test arbitrary positions on?