lichess.org

4 moves

no castling rights info is provided so i'll say
1. e4 e6 2. Bb5 Ke7 3. Bxd7 c6 4. Be8 Kxe8

there are plenty of ways.
For example:
1. e3 c6 2. Bd3 e6 3. Bc4 d5 4. e4 dxc4

Rule number 1 = reach the position
Rule number 2 = do it in 4 moves for each
Rule number 3 = still possible castling

Applies to mine solution.

Reconnecting