No, touching feet is not a sin.
If you mean touching like touching a buttock or a breast then yes that is lust.Do not do that that is foolish.
The same reason boys get jealous about guys touching their girlfriend. Sexual jealousy.
Yeah we like touching girls but that's if the girl wants to be touched. Ask before touching. Always.
Because girls like guys with big muscles :)
Some girls are fine with it but others don't enjoy it.
If she is your wife then that's no problem. But if not then yes its a sin.
only when they initiate it
Yes, they do, if they are heterosexual that is.
touching little girls
yes it is