exchange questions

Hello! I am currently a freshmen in soss.

1. when do students usually go for exchange (y2? y3? and which term).
2. where do they usually go? (im interested in going to EU)
3. what are the mods recommended to keep for exchange mapping? (eg. if I'm interested in taking a language mod, does that mean I can't use it for mapping)
4. additionally, I would like to join OCSPs and was wondering it it would clash with exchange periods etc?

Thank you!