No difference. The "to" is usually understood.

It can depend on sentence structure. It's interchangeable if the sentence reads as follows: "I have something to give to you." or "I have something to give you." However, you would commonly say "I need to give you something." rather than, "I need to give to you something."

Thank you, Professor B! :)

This is from my book, "keys to words": to 15. used with words that show action (to run, to go, etc.) or words that show being (to be, to seem, etc.) to has no meaning but helps identify the word it is used with: He likes to play. (He likes playing.) To work hard is very important. (Working hard is very important.)