Three-check: best lines by SF9+

Well, according to Stockfish 9+, white starts and wins cuz the evaluation of the initial position is +1.6 at depth d=35. 

1 ply:

• 1. Nc3 (+1.6) 
• 1. e4 (+1.6)

2 plies:

• 1. Nc3 e6 (+1.9)
• 1. Nc3 c5 (+2.0)
• 1. Nc3 Nc6 (+2.2)
• 1. e4 e6 (+2.0)
• 1. e4 Nc6 (+2.2)
• 1. e4 c5 (+2.2)
• 1. e4 b6 (+2.3)
• 1. e4 c6 (+2.4)

(to be continued)

Weird. What tweaks did you do so Stockfish thinks of giving 3 checks instead of checkmate?

Stockfish for three-check is available on lichess. 

And why ?  It's not forbidden to use engines in order to prepare in advance your opening repertoire. 

Have you tried leaving Stockfish on for 24 hours to see if it calculates a forced mate? Lol

You should put Stockfish vs Stockfish and create your own Alpha Go but this time it will be called 

"Tria go".

You mentioned another chess site!!!

LoL It might be a good idea. 

Simple mentions are not forbidden. I didn't put neither external links nor advertising (I just answered a question). 

Is three check a forced win for white? 

Absolutely (95%), the evaluation +1.6 at depth equal to 35 plies speaks for itself. 

3 plies: 1. Nc3 e6 2. e4

SF9+ suggests: 2...Nc6, c6 (+1.2), Bb4, Nf6 (+1.3). 

for black nc6 or c5 is best in terms of surprise value and stuff