Yesterday he said John will/would come here tomorrow.
Both are possible.
Peter intended to marry when he is/was 28.
The use of the past-tense form 'intended' suggests that he no longer intends this. Only 'would' works for me.
What would you do if you win/won the game?
The use of 'would' after 'if' makes this a less likely hypothetical than 'will'; this needs to be reflected in the past-tense form 'won'.
Student or Learner