Can I have 2 iCloud accounts on one phone

An iPhone can only have one Apple ID signed into it at any one time. Switching between IDs is not very easy or else there may be mixing of data. If you sign out of one ID and sign in with another you will be asked if you wish to retain data from the previous account. If you say yes, there will be mixing of data from the old account on the phone into the new account (but not vice versa). iPhones are really only designed for use by one user unless you decide to give it to another person for long-term use. In that case, read What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

No. Your device can be connected to a single ID. If you log out and then into a new ID, your data will be merged unless you reset and erase your device first.