I think we need to pause here a minute.
The preposition generally used and translated 'for' in the relevant passages is 
huper, which means 'on behalf of.' as in Galatians 2:20 and 3:13. for example   Now if I buy pay a bill on your behalf (not likely to happen!), I pay it and you don't.  If Christ suffers on our behalf, He suffers and we don't.  That is substitution and if a penalty is involved, it is penal substitution.  Let's look at Galatians 3:13.  
Christ has redeemed us from the curse of the law, having become a curse for [Gk. 
huper] us.'  He becomes a curse and we don't.  That's penal substitution. 
 
There are some places where the preposition 
anti is used.  It tends to mean 'over against' or 'instead of.'  Luke 11:11. 
'...Will he for [Gk. 
anti. 'instead of''] 
a fish give him a serpent?'  Now look at Mark 10:45 or Matthew 20:28. 
'.....And give His life a ransom for [Gk. 
anti]
 many.'  The ransom is paid to God's justice.  Christ pays it; we don't. Penal Substitution.
There are several other Greek prepositions translated 'for' but I think these two are the most important.