England named a 22-man party on Thursday for that match and a fixture against Mexico at Barnet four days earlier.
Southampton midfielder Stephens, who is currently on loan at Swindon Town, is named in the under-20 squad for the first time.
The former Torpoint schoolboy made five appearances for Argyle before moving to Southampton in 2011.
Truro-born goalkeeper Walton was also on Argyle’s books before moving to Brighton & Hove Albion.
Tickets for the match at Home Park on March 29 are just £3 for adults and £1.50 for concessions.
ENGLAND UNDER-20 SQUAD
Goalkeepers: Christian Walton (Brighton & Hove Albion), Jordan Pickford (Sunderland)
Defenders: Dominic Iorfa (Wolverhampton Wanderers), Moses Odubajo (Brentford), Dominic Ball (Cambridge United – loan from Spurs), Baily Cargill (AFC Bournemouth), Kortney Hause (Wolverhampton Wanderers), Jordan Turnbull (Swindon Town – loan from Southampton), Harry Toffolo (Swindon Town – loan from Norwich City)
Midfielders: Harrison Reed (Southampton), Jack Barmby (Leicester City), Jack Stephens (Swindon Town – loan from Southampton), Jamie Hanson (Derby County), Lewis Baker (MK Dons – loan from Chelsea), Matty Grimes (Swansea City), Ben Osborn (Nottingham Forest), Alex Mowatt (Leeds United), John Swift (Swindon Town – loan from Chelsea)
Forwards: Callum Robinson (Preston North End – loan from Aston Villa), Chuba Akpom (Arsenal), Kwame Thomas (Derby County), Chris Long (Brentford – loan from Everton)