Restricting access to a single MultiSite site based on IP — possible?

Don’t know about more extensive solutions but this can be accomplished with tiny plugin which will check IP (in $_SERVER) at some stage of load and die on match.

Had you looked through official repository? There is IP tag.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)