RECOMMEND 

vs  SUGGEST

transitive verb

VIDEO 

English Grammar | Suggest vs. Recommend

sug·gest·ed, sug·gest·ing, sug·gests

1. I recommended my friend to try the shark fin soup <<< Correct the sentence.
2. I recommended the shark fin soup to my friend. << Is it correct? (Not quite. Use the word 'try')

1. I recommended my friend (to) try the shark fin soup. << Why is it correct? Because the word try is the subjunctive mood. 
2. I recommended (that) my friend try the shark fin soup. (Not to try, just try) conj. that is optional
3. I recommended (that) my friend try the shark fin soup.

this construction is called the subjunctive mood. 

1. I wish I was rich >> I wish I were rich. (was >> were) use plural verb -- (try is a plural verb)
2. I suggested (that) my friend try the shark fin soup.
3. I suggested (...) my friend try the shark fin soup.

So what is the difference between suggest and recommend?

In English, very often two words can be synonyms, and in most situations, they can be interchangeable. but in a few situations, they are not interchangeable.